Full disclosure, I'm looking at this as a Canadian citizen.
I have been a rock solid supporter of president Trump since 2016. I cannot think of a single issue where I did not support him 100%. Sure, like others I would sometimes cringe a little at some of his choices of words, but not at his intent. That said, tariffs on Canada, are not so much a favorite of mine. Now before you get your shorts in a knot with "Oh now that it's affecting you...", let me explain.
I will grant you the following points; (i) Canada has an absolute idiot of a leader who has hung around longer than the odor of forgotten used gym clothes in a locker room. (ii) Canada has benefitted from a trade surplus with the United States for a long time (iii) Canada does not contribute to NATO the way it should (see point (i) for the reason why) (iv) Canada has not done enough to secure it's border with the United States.
ALL TRUE.
Furthermore, president Trump did offer Justin Trudeau an easy out of the tariff problem; secure the border. It's not a crazy ask, and it's something Canada should want just as much as the U.S.
But alas, "unintended consequences" rears it's ugly head as it always does. President Trump no doubt had hoped this pressure would hasten the demise of Justin Trudeau. That's a truly laudable goal. Justin Trudeau is despised in Canada. But what has happened instead of Trudeau caving, he's donned his faux tough guy cape, and so has most every politician in Canada (with a few key exceptions), and the mood has gone straight to that of dig in and fight back. Worse, it appears the Liberal party of Canada might actually benefit from the tariff fight. Instead of waiting a few months for a leader that is much more aligned with Trump, this may actually prevent Pierre Poilievre from winning the election. Worse still, Poilievre knows it and has had to start talking tougher on Trump in order to not cede ground on what was a 99% certain blowout win against the Liberal party in the coming months. In otherwise, a soon to be allied leader, has had to drift in the opposite direction.
Secondly, for a country full of people who despise Trudeau, and generally have strong positive feelings about the United States, both of those notions are already in jeopardy. While as an American you might not care what Canadians think of you, it's not without consequence. Keep in mind, Canada is still an American ally; we're not Iran. Heck we're not even Mexico in terms of illegal immigration or drug flow or danger to the U.S. That is not say there's no culpability on Canada's part, but in terms of proportionality my point remains; Canada is no Mexico.
My point on Canada being an ally is threefold. If Trump is seen to be bullying allies like Canada, what does that mean for the U.K., Australia, and other erstwhile allies? Maybe you still don't care, but don't be surprised if taken to it's logical conclusion, America does indeed end up being isolated. No matter how powerful a nation might be, that's a precarious position.
Thirdly there's trade. Canada thanks to Let's Go Brandon's killing of the Keystone pipeline, has a new pipeline to the Pacific being built. It's not just about the U.S. not needing Canadian oil and gas, it's about to whom else can Canada sell it's resources. Japan, Korea. Maybe, but the most interested buyer is China. Canada would highly prefer to sell to the United States. But Trump is effectively pushing an ally into the arms of a mutual geopolitical enemy, and potentially helping that enemy.
Fourthly, Trump's approach does not distinguish between the Canadian people and Canadian 'leadership'. It's the former who will be adversely affected by this. Justin Trudeau doesn't give a damn and you can tell by his 'tough guy' response. Common sense would dictate fix the border. But there's no common sense with Trudeau, only ego. Conflating Trudeau with the average Canadian (who is already viciously hammered by bad economic leadership and struggling day-to-day to get by) is not a good look.
And all of that is just surface level. From a Canadian perspective there's a lot more to this. But bear in mind I have been blogging pro-America for a over 15 years and pro-Trump posts since he ran for president in 2016. I'm second guessing his approach to Canada specifically, imagine how other, less pro-American, Canadians are thinking.