Mark Carney called it an extreme tail risk. That is finance talk for a very rare event that would cause enormous damage if it ever happened. The Canadian prime minister told The New York Times his government has examined the possibility of US military action against Canada. He said it would be irresponsible not to prepare, even if the odds are remote.

You hear that and your brain does a little skip. The United States and Canada share the longest undefended border in the world. They are allies. They trade. They fight in the same wars. The idea of one invading the other feels like something out of a fever dream.

But here is the thing about tail risks. You do not plan for them because you expect them. You plan for them because the cost of being wrong is too high. Carney knows this better than most. He ran the Bank of Canada. He ran the Bank of England. He spent his career thinking about what could break the system.

The prime minister described the risk of an action by the country’s southern neighbour as remote. That word matters. Remote does not mean impossible. It means far away. It means unlikely. But in his job, unlikely is not the same as ignorable.

Carney said his administration has carefully examined what would happen if the US took military action against his country. He did not give details. He would not say what preparations were made or what scenarios were run through. That part stays quiet. What he did say was clear enough. Leaders have a responsibility to look at extreme tail risk. That is just risk management.

This did not come out of nowhere. President Donald Trump has talked about Canada becoming the 51st state. He has said it more than once. In January 2025 he ruled out using military force to annex Canada. But he also said he would consider using economic force to push Canada toward joining the United States. Trade talks between the two countries collapsed last month. Tariffs went up on both sides. The relationship has gotten tense.

Even with all that, Carney told the Times he speaks with Trump frequently. They have a direct line. They talk. The two men have spoken often, even since trade talks fell apart. That is worth holding in your head while you think about the rest of it.

The White House responded quickly. A US administration official said Trump has done more than anyone to protect Canada from threats. That was their answer to Carney’s remarks. Defence Minister David McGuinty played it down on the Canadian side. He told reporters it is normal for all militaries to spend time analyzing risk scenarios. When asked about the probability of a US attack, he called it a tail risk, just as the prime minister had said.

And this is where the story takes a turn that comes back around. Carney is not just talking about military action in the abstract. He is talking about reducing Canada’s reliance on the United States for key technology. From space satellites to fighter jets. He described in detail how his government is systematically working to make Canada less vulnerable to American threats. That is the practical side of thinking about tail risk. You do not just imagine the worst case. You change what you depend on.

Canada’s strong economic ties to the United States were once a strength. Carney has said they are now a weakness that must be corrected. The world is more dangerous and divided, in his view. The US has changed its approach to trade. Tariffs are at levels not seen since the Great Depression. Many former strengths based on close ties to America have become weaknesses.

You can hear the caution in how officials talk about this. McGuinty said analyzing risk scenarios is routine. Carney said the scenario was not the expected outcome. The White House said Trump has protected Canada. Everyone is saying the same thing in different ways. The risk is remote. The preparation is responsible. The relationship is complicated.

There is a moment in this where the humor runs out. Two countries that have not fought each other in more than a century. A border that stretches for thousands of miles with no fortifications. Generations of Canadians and Americans who have lived, worked, and married across that line. The idea that one might attack the other is not just unlikely. It is hard to picture.

And yet Carney sat in a room at The New York Times and said his government has examined it. He used the language of finance because that is the language he knows. Extreme tail risk. Not a base case. Irresponsible not to prepare. Those are not the words of someone who expects an invasion. They are the words of someone who has seen what happens when people ignore low probability, high impact events.

The defence minister called it normal. The White House called it unnecessary. Carney called it responsible. All three can be true at once. Militaries do analyze scenarios that will never happen. Leaders do prepare for things they do not expect. And allies do sometimes say things that make each other uncomfortable.

What remains unknown is what Canada actually did in response to this assessment. Carney declined to discuss in detail what the examination involved. He would not say what contingency plans were considered or what changes were made. That silence is its own kind of answer. Some preparations are not meant to be public.

The prime minister paused when he talked about this. You could hear it in the quotes. We were attacked. You are at war when you get attacked. That was from an earlier interview, but it sits next to this one. Carney has settled into a role he warned was necessary. A leader standing up to an erratic adversary. He has called Trump an adversary in so many words. He has said Canada was attacked, economically at least.

So you have a prime minister who says the risk of US military action is remote. You have a president who says he has done more than anyone to protect Canada. You have a defence minister who says analyzing these scenarios is normal. And you have a border that stays open, day after day, while all of this gets said out loud.

The world is more dangerous and divided. Carney said that. Maybe he is right. Maybe he is being careful. Maybe both. What is clear is that he has put the possibility of US military action against Canada into words. He has called it what he thinks it is. An extreme tail risk. Not worth ignoring. Not worth expecting. Just worth preparing for, because that is the job.

Explore: Outdoors