Carney admitted last week that he had prepared for the scenario, telling the New York Times he had a responsibility to consider all possibilities. "That's just risk management," he said.
Trump's global tariffs and his often-repeated desire to make Canada the 51st state have led Canada to war-game an attack by the Americans. In 2025, Trump said it was "highly unlikely" the US would ever use force against Canada, saying instead he would continue to exert economic pressure to obtain political aims.
The White House told the BBC this week: "President Trump has done more than anyone to protect the great people of Canada."
Military experts who spoke to the BBC believe an invasion is a long shot, pointing to the many ways the two countries work together on defence. Lt-Gen Christopher Coates, a former officer of 34 years with the Royal Canadian Air Force who held senior positions, said a war between the two countries would be complicated and almost difficult to imagine.
"I was involved in military operations for my whole career, and we never considered the possibility that there would be a military attack coming from US territory," he told the BBC.
Coates, who served on Nato missions, noted that Canada and the US collaborate on many aspects of military defence and are both members of the alliance, which mandates members to defend a fellow member-nation should they be attacked.
But the issue is clearly weighing on Canadians' minds. In January, after the US captured Nicolás Maduro in Venezuela, a Leger poll suggested that over 30% of Canadians believed that a US invasion was likely.