Trump’s follow-through on his threat of steep tariffs – which were long speculated to be a negotiation tactic to get concessions on border security – have bewildered Canadians, who have enjoyed close economic, social and security ties to the US for decades.

“It’s a shock,” Michael Ignatieff, the former leader of Canada’s Liberal Party, told the BBC.

“We’re into a new world, in which the question on whether you can trust America becomes the fundamental question in foreign policy for every country.”

Pierre Poilievre, leader of Canada’s opposition Conservative Party, called the tariffs on Sunday “massive, unjust and unjustified.”

“Canada is the United States’ closest neighbour, greatest ally and best friend,” he said, noting that Canada fought alongside the US in two world wars, as well as in Korea and Afghanistan. “There is no justification whatsoever for this treatment.”

Prime Minister Trudeau questioned in his Saturday address why the US would target Canada instead of looking to “more challenging parts” of the world.

A portion of his speech was directly addressed to Americans, and he too, pointed to a history of shared bloodshed. “We have fought, and died, alongside you,” Trudeau said.

Thomas Juneau, a professor at the University of Ottawa with a focus on national security, told the BBC that Trump’s tariffs “undoubtedly represent an earthquake in Canada-US relations.”

“This is extremely destabilising for Canada,” Prof Juneau said. “As a country, we have massively benefited from our extremely close trade and security partnership with the US for decades.”

While the trade battle would likely force Canada to look for partners elsewhere, it ultimately can’t escape geography, he said. It will remain reliant on the economic superpower next door.

“That is why Canada must absolutely now focus on salvaging the relationship as much as possible,” Prof Juneau said.