David McMillan, the co-owner of Montreal’s famed temple of gluttony, Joe Beef, used to spend his days obsessing over his signature dishes like rabbit with mustard sauce, and lobster spaghetti. These days, however, he has another preoccupation: Studying American vaccination rates.

Before the pandemic, so many American gastronomy pilgrims from New York, Boston and Los Angeles came each week to Joe Beef that many local residents, facing a 10-week waiting list, all but gave up trying. The Americans, Mr. McMillan recalled wistfully, thought nothing of buying expensive bottles of Champagne and sucking down oysters until midnight, before purchasing his prophetic-sounding cookbook “Surviving the Apocalypse.”

“Ah, how I miss the Americans,” said Mr. McMillan, who presides over a mini-empire of four restaurants in the city, including Liverpool House, where Justin Trudeau once bromanced President Obama. American tourists, he added, accounted for half of Joe Beef’s pre-pandemic weekly revenue of about $118,000, or about 150,000 Canadian dollars. “When the Americans were here every night it felt like we were putting on a Broadway show.”

“Now, I look every day at how the U.S. vaccination is going,” he added. “And I get messages every day from American clients asking when they can get back in.”

It’s a question many in the Canadian tourism industry have also been asking, ever since the Canada-U. S. border was closed to nonessential travelers in March. The loss of American visitors, armed with their strong dollars and consuming zeal, has buffeted popular destinations like Montreal, Quebec City and Vancouver, already reeling from a debilitating pandemic. Canadian airlines have been forced to make thousands of layoffs.

More than two thirds of the 21 million international tourists who came to Canada in 2019 were from the United States, according to government data, with Americans pumping about $8.7 billion into the economy. That’s compared to the nearly $1.3 billion spent by Chinese visitors, about $1 billion by Britons and about $735 million by the French.

Absence makes the heart grow fonder — but not enough to open borders.

Canadians have long had a love-hate relationship with their larger, showier neighbor south of the border. That ambivalence was magnified during the Trump administration, when the mercurial American president slapped punishing tariffs on the country, suggested Canada had burned down the White House during the War of 1812 (the country didn’t then exist) and called its prime minister, Justin Trudeau, “very dishonest” and “weak.”

But it has always been more love than hate when it comes to travel between the two countries, with Americans drawn by Canada’s proximity, its common language in most regions and its mix of cosmopolitan cities and natural landscapes.

The inauguration of President Joe Biden and Vice President Kamala Harris, who spent her disco-dancing teenage years in Montreal, has renewed the ardor between the two allies, while vaccination has created cautious optimism about taming the pandemic.

Still, while the tourism industry is experiencing one of its worst crises since World War II, recent polls show that the vast majority of Canadians want the borders to remain closed. Canadians, a typically rule-abiding people with a deference to scientific authority, have looked with some horror at the spiraling infection rates in the United States, and the handling of the coronavirus during the Trump administration.

Mélanie Joly, Canada’s minister of economic development, who is responsible for tourism, said keeping the borders closed was a matter of pragmatism. “We can’t talk about reopening the economy until we stop the spread of the virus,” she said in an interview. Lamenting the absent Americans, she added: “It’s a bit like losing your best friend but you are sick and your best friend is sick and everyone is better off staying at home.”

She said she hoped the travel industry would be “back on its feet” by September, as vaccination in Canada and the United States accelerated. The border, she stressed, would remain closed until the pandemic is contained.

At the Musée d’Art Contemporain de Montreal, American museum-goers from New York, Massachusetts and Vermont helped turn a pre-pandemic exhibition on Leonard Cohen, the gravelly-voiced Montreal-born balladeer, into a blockbuster. But the museum’s director, John Zeppetelli, said knowing friends and colleagues in the art world who had contracted the virus while attending art fairs last year in the United States and elsewhere had underscored the need for caution. “Public health has to supersede economic concerns,” Mr. Zeppetelli said.

Covid-19 tests, quarantines and a cruise ship ban create obstacles to travel.

As it is, Canada itself is experiencing a lethal second wave, with a curfew in effect in Quebec, a lockdown in most parts of Ontario, the country’s most populous province, and border restrictions in each of the country’s Atlantic coast provinces that have required even Canadians from other provinces to quarantine.

“The general public is not concerned about the tourism sector, they don’t want to see Americans or French or Germans, for that matter,” said Frederic Dimanche, director of the Ted Rogers School of Hospitality and Tourism Management at Ryerson University in Toronto. “The Biden administration is seen as a welcome change. But the vaccine isn’t a cure-all since it will take months to roll out.”

Americans who want to visit Canada will find many obstacles.

Since Jan. 7, travelers arriving on international flights to Canada, including Americans who have dual citizenship or an immediate family member who is Canadian, have had to show a negative Covid-19 test, conducted within 72 hours before departure. Under new rules, they will need to be tested again upon arrival and wait for three days at their own expense in an airport quarantine hotel at an estimated cost of about $1,575. Anyone who tests positive will have to quarantine elsewhere for 11 more days.

The Canadian government has also banned cruise ships with more than 100 people from Canadian waters until February 2022.

A backlash against foreign travel in both directions of the border has also been fanned in recent months in Canada after a slew of politicians were caught sneaking away on sunny vacations. Among them was Ontario’s former finance minister Rod Phillips, who was forced to resign in December after posting a recorded Christmas Eve video message on Twitter. The video showed him sitting next to a fireplace, wearing a sweater and downing eggnog, while he was, in fact, on vacation on the French island of St. Barts. Canadians, forced to stay at home, were irate.

Travel shaming has also been directed at the thousands of Canadian snowbirds who have traveled to the United States during the pandemic, decamping to Florida and Arizona, among other places. They have been circumventing American land border restrictions by traveling by plane and shipping their cars and pets separately.

The loss of American tourism dollars is a blow.

In Canada, the lonesomeness for the Americans has nevertheless been acute in many quarters, their absence felt in eerily vacant city squares, empty shops or shuttered theater and music festivals where American visitors have long been counted among the most ardent and attentive guests.

At Ontario’s famed Stratford Festival, where the high culture of Shakespeare mingles with more populist productions like “Little Shop of Horrors,” the forced cancellation of the 2020 season and the loss of American visitors hit local bed-and-breakfasts and restaurants as well as shops selling “To Bieber or Not to Bieber” T-shirts celebrating the city’s famous local son Justin Bieber.

The festival’s executive director Anita Gaffney said the loss of American theatergoers had dealt a huge blow, since Americans made up a quarter of the festival’s 500,000 paying customers. The Americans, she added, stayed the longest, thought nothing of seeing seven plays in a week, and included many committed Shakespeare mavens who could recite esoteric passages from Pericles.

“The Americans not being here has had a big impact on the local economy,” she said, noting that the festival had tickets worth about $15.8 million that it had to refund or hold over until this year.

Among the Canadian cities missing American visitors is Quebec City, the only fortified city north of Mexico, in North America whose walls still exist. Its picturesque old quarter, 18th-century churches, winter carnival and ramparts have long drawn Americans, and luminaries like Grace Kelly, Bill Clinton and Alfred Hitchcock have visited. In 1953, Hitchcock filmed part of “I Confess,” his noirish murder mystery, at the city’s castlelike Fairmont le Château Frontenac hotel.

Maxime Aubin, a marketing manager at the hotel, said it was suffering from the lack of Americans, who usually accounted for half the hotel’s occupancy, most often reserved the hotel’s two most expensive Churchill and Van Horne suites — which cost about $2,363 a night — and stayed the longest among nationalities at the hotel.

To offset the loss, he said, the hotel, which rises above the St. Lawrence River, had been trying to attract more Canadians by retooling the hotel as a “cruise ship experience,” complete with ocean views, cooking classes and all-you-can-drink open bars.

In addition to a temperature-taking station at the entrance of its grand lobby and elegant hand sanitizer dispensers at check-in, the hotel has been offering pandemic discounts, including slashing the price of the suites by half at one point last summer, and offering other promotions like two nights for the price of one.

In Montreal, which has long attracted American tourists drawn by its European flair, libertine spirit and events like the Canadian Grand Prix and International Jazz Festival, Yves Lalumière, chief executive of Tourisme Montreal, the city’s main tourism body, said the city had lost at least $550 million because of the absence of American guests. He was hoping for “revenge spending by American visitors after months of privation” when the borders finally opened, hopefully by summer.

Not all the Americans are missed.

Some downtown residents in Montreal said they didn’t miss the large gaggles of raucous American alcohol and pot tourists, who used to come on weekend benders to take advantage of Quebec’s strip bars, drinking age of 18 and government-owned shops selling pre-rolled marijuana joints.

Philippe Orfali, a longtime downtown resident, observed that the decrease in the number of American tourists had also helped tame the area’s Airbnb rental frenzy and had forced many apartment owners to put their short-term rentals back on the long-term rental market. “This should come as good news in a city that has been struggling for years with a housing shortage,” he said, even as he added that rental prices had remained relatively high.

Mr. MacMillan, of Joe Beef, said the loss of the Americans, while painful, also had some advantages, allowing the restaurant to reconnect with local residents, who have been ordering takeout while indoor dining is banned. Without having to cater to the sometimes squeamish culinary tastes of his American guests, he has brought back some of his favorite items, like pig cheeks and kidneys.

In British Columbia’s pristinely beautiful Okanagan Valley, an ascendant wine region that draws American tourists from across the west coast, John Skinner, owner of Painted Rock Estate Winery, lamented that not being able to host American weddings on the grounds of his winery, or to attract American oenophiles, had dented business.

But he said that the loss of the Americans has been more than offset by the proliferation of Canadians doing staycations. Local hotels had seldom been more packed with visitors from Vancouver and the rest of Canada, he added.

“The hotels and restaurants have been full of Canadian wine-tourists, so I can’t say we have missed the Americans.” He quickly added: “We love Americans. But they can come visit us when they are all inoculated and we are, too.”

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