TORONTO — As Canadians absorb President Donald Trump’s trade war and his threats to make Canada the 51st state, one thing has become clear: One of the world’s most durable and amicable alliances — born of geography, heritage and centuries of common interests — appears to be broken.

Canadians say they are feeling an undeniable sense of betrayal after Trump declared a trade war against America’s northern neighbor and longtime ally. Trump keeps threatening Canada’s sovereignty and vowing to put sweeping 25% tariffs on Canadian products, though Canadian Prime Minister Justin Trudeau said Monday that the tariffs will be postponed by at least 30 days after he promised more cooperation on the border.

In Canada, discussion and disapproval are everywhere.

Canadian hockey fans have been booing the U.S. national anthem at recent National Hockey League games. Addressing the nation this past weekend, Trudeau channeled the betrayal that many Canadians are feeling, reminding Americans that Canadian troops fought alongside them in Afghanistan and helped respond to myriad crises from wildfires in California to Hurricane Katrina.

“We were always there standing with you, grieving with you, the American people,” he said.

The Canadian jitters, some worry, could go beyond the moment.

“The damage is going to be long lasting,” said Robert Bothwell, a professor of Canadian history and international relations at the University of Toronto. “The Americans won’t be trusted anymore. The 51st state stuff is just contemptuous.”

The ties between the countries are without parallel.

Nearly $2.5 billion worth of goods and services cross the border each day. Canada is the top export destination for 36 U.S. states and 77% of Canada’s exports go to the United States. Each day, about 400,000 people cross the world’s longest international border. There is close cooperation on defense, border security and law enforcement, and a vast overlap in culture, traditions and pastimes.

“He wants to come after us?” said Doug Ford, the leader of Canada’s most populous province of Ontario. He has said that it feels like being stabbed in the heart by a family member. “I’ve yet to hear one American citizen say Canada is the problem,” he said.

Some Canadians are circulating lists of Canadian products they can buy instead of American items and others are canceling vacation plans to the United States. The U.S. Travel Association said the tariffs on Canada could impact Canadian visitation to and spending in the United States, noting that Canada is the top source of international visitors to the United States, with 20.4 million visits last year.

“What he is doing now is unprecedented and highly damaging for the relationship. ... He is eroding Canadians’ trust towards the U.S. in ways that will make it hard to repair the relationship,” said Daniel Beland, a political science professor at McGill University in Montreal. He says many Canadians feel betrayed by Trump’s threats and attitude.

“It’s certainly one of the worst moments in Canada-U.S. relations since the creation of Canada in 1867,” Beland said. “His talk about making Canada the 51st state is a direct attack against the country’s sovereignty. Even if we exclude that threat, he shows no respect for Canada’s sovereignty and institutions.”

Canadian officials said they would apply 25% retaliatory tariffs to U.S. imports including beverages, cosmetics and paper products. A second phase will be even more punishing.

Trump and Mexican President Claudia Sheinbaum put their planned tariffs on hold Monday for a month to give time for further negotiations, and Mexico said it planned to deploy 10,000 members of its national guard to address drug trafficking.

Trudeau noted that the United States and Canada have built the most successful economic, military and security partnership the world has ever seen — a relationship that, he says, has been the envy of the world.

“As President John F. Kennedy said many years ago, geography has made us neighbors. History has made us friends, economics has made us partners and necessity has made us allies,” he said.

Trump also plans to put a 10% tariff on Canadian energy. Underscoring the potential effects, Canada provides more than 4.3 million barrels of oil a day to the United States. The U.S. tends to consume about 20 million barrels a day, according to the U.S. Energy Information Administration. It has been producing domestically about 13.2 million barrels.

Yet Trump keeps saying the United States doesn’t need Canada for anything and said again Monday that he’d like to see Canada become the 51st state. And his vice president dismisses Canada too.

“Spare me the sob story about how Canada is our ‘best friend.’ I love Canada and have many Canadian friends. But is the government meeting their NATO target for military spending? Are they stopping the flow of drugs into our country?” Vice President JD Vance posted on X.

Canada announced a billion-dollar plan to secure the border even though far fewer migrants and less drugs enter the U.S. through Canada than Mexico.