As is typical of these discussions, there’s an overemphasis here on consumer products.
The vast majority of cross border trade, and in fact the majority of all business ever conducted in general, is business to business. I am a consultant working with many, many businesses; NONE sell direct to the consumer. Not a single one. The inflationary effect of a general tariff is, to almost all people, something felt indirectly; prices will go up because of a general supply shock. Of course some is pretty direct but most is not.
Most Americans (or Canadians for that matter) don’t even know what potash is, but a huge amount of it is exported from Canada to the USA. Potash is an absolutely irreplaceable product, a critical precursor in the production of fertilizer. The USA cannot stop importing it because you cannot just dig a potash mine tomorrow, there is no practical alternative, and Canada is the biggest producer of it in the world. If it’s tariffed, that is a deadweight loss for the American economy; it is quite literally the government taxing farming. Food prices will go up on food grown in the USA. It is absolutely inevitable. Furthermore, the USA’s fertilizer sales abroad will be hurt by a huge potash price hike, further damaging that industry.
Worse are the cross border movements of a zillion things. Last week I was working at a company that makes lead shielding for the medical industry. Many of their clients are American. Those clients will now be paying 25% more - or they won’t be able to meet their construction schedules. Companies that are good at lead poured products just do not grow on trees, and a tariff either means the medical industry pays more, or they don’t get stuff done. You’ll pay for that in a hundred hidden ways.
To answer the OP, the OP is in a sense right. Economically speaking the best thing Canada can do is raise no tariffs at all. Tariffs are a case of “I will hurt myself to hurt you.” But POLITICALLY, there is little choice; punching back, while it hurts us, may be better in the short run. (I’m not even getting into the possibility that Ontario and Quebec will retaliate but adding a huge rate hike to the electricity they sell to the US northeast.) The American consumer is generally ignorant and won’t know why prices are soaring, but they do complain to their congresspeople and governors. Congresspeople and governors do not like angry constituents, they like happy constituents. They don’t like business leaders on the phone and in their office screaming in anger over massive price shocks. Targeted tariffs meant to increase the number of furious phone calls and emails to congresspeople and governors are smart moves, meant to accept a bit of short term pain in an effort to speed up the pressure on the White House to drop general tariffs.
This is all an unnecessary catastrophe that will hurt people in both countries, and I suspect much of it is due to oligarchs seeing a way to profit from the pain of the working class. As has been pointed out, the USA is becoming an existential threat to Canada and we have no choice but to fight. It’s a matter of our independence and, frankly, there is something to be said for pride and honor.