Trump respects a blunt display of force...

Canada could mount any number of such blunt force responses. The US probably has more. The problem is, if you're in a situation with two entities both triggering blunt displays of force, you're in a bad situation. The proper response to the saying "Never bring a knife to a gunfight" is "Why on earth would you want to be in a gunfight?"

But if given no choices, what would a reluctant Canuck reach for? One that springs to mind is that 92% of all potash used in the US is imported, and close to 90% of that comes from Canada. (most of the rest from Russia I think--more of a geopolitical friend to the US than Canada these days).

Canada, on the other hand, has a number of enthusiastic export markets for the stuff--the US gets only around half of the exported volume at present. So an outright ban on shipments of potash to the US would get the attention of a large number of US farmers. Especially the wheat and corn crowd. Some farmers vote, though that may not be as important as it once was.

Jim