I think a retaliation for a tariff should be an export tax. Let's say Canada puts a 50% export tax on maple syrup unless the car tariff is withheld
I also had this idea, but it can't be something you can get in another place. But for something like potash it might work.
But I think overall it does not really matter. A war is a war, so there will be no real winners.
Here we go again.
It would be the most effective way to hurt Americans.
But it isn’t politically possible for Canada to do this. The two segments that would be most effective, oil & gas and potash happen to come from provinces that already have significant issues with the federal government. One is even flirting with separation, which would be inflamed by export taxes.
Canada is also very venerable to similar actions by the Americans. Refined oil products, fertilizers and oil & gas pipeline transit all come from the Americans.
It is fun to imagine Canada sticking it to the Americans with export taxes, but it will never happen.