Canada

I think you're maybe misunderstanding the direction of the tarrifs costs?

The tarrifs cost American importers regardless of our counter tarrifs. For an example, the article pointed to, Target which

said it expected to raise prices within days, specifically mentioning Mexican strawberries, bananas and avocados

Doesn't matter what counter tarrifs Mexico puts in place, produce from Mexico will be more expensive in America. Counter tarrifs just make things more expensive in our own country and hopefully dissuade people from buying them.

The markets aren't roiling because of reduced access to Canadian markets, it's that the stuff in their own products (like say, car parts made in Canada) overnight became 25% more expensive. (I would also be surprised if we tarrifed much in our shared industries like auto production as it'll be hard enough to keep those factories here without making them even more expensive.)

That's not to say what we do is irrelevant, we should absolutely boycott and do whatever we can to make the markets worse but it's good to do so with clear eyes.