The real problem is that Trump's supporters don't understand tariffs, and wouldn't believe the explanation anyway because to them it just sounds like Orange Man Bad.

When the US imposes a tariff on Canada, importers of Canadian goods pay the tariff to the US government. To recover that cost they raise the prices they charge American customers. So Americans end up paying the tariff. The only damage it does to Canada is that the tariff could discourage US importers from buying certain goods from Canada if they can get them somewhere else without paying a tariff. That happens in some cases, but in others Canada is already the cheapest (or only) source of a high-demand item, so Americans will just pay the higher prices - the way they're still paying jacked-up COVID prices for so many things, for example.

Millions of Americans, being too dumb or unwilling to grasp this, think these tariffs are Trump heroically saving them from the evils of foreigners who want to destroy their Freedom.