Imagine the following scene: you are seated with another individual at a table in a nice restaurant. For whatever reason, you enter into a heated and bitter argument. Voices get raised. At some point, your companion reaches into a bag and pulls out a hammer. He then proceeds to smash himself with it, hard, on the forehead. So much so that he now bleeds profusely, with a deep and visible cut over his left eye.
I don’t know exactly how you would react to such a situation, but I doubt very much that you would grab the hammer out of his hands and proceed to hit yourself in the face even harder as a “retaliatory measure” to what your interlocutor just did to himself. That is, assuming a minimum level of sanity on your part.
Well, for Canadian governments to retaliate to potential tariffs to be imposed by the Trump Administration with tariffs or blockades of their own against American exports would be just as unproductive and misguided as you hitting yourself in the face with that hammer.