I really doubt Canada as the upper hand in such talks but I also agree with not caving in and accepting whatever consequences...
It's not an upper hand, just a different kind of consequence.
Conservatives will still shit all over Trudeau, but his only other option is to cave, that will also have conservatives shitting all over him. That will also lead to cheeto trying this tactic again. It will be a painful process, but war has casualties.
On Trumps side, he has bleaker options.
If he continues with the tariffs, it is going to cause massive problems in the U.S. markets. GM especially will plummet, leading to huge layoffs and more expensive cars. Whether the number of cuts.is enough to trigger a recession will need to be seen. Keep in mind the domino effect. Less cars means less steel and aluminum jobs to supply these chains. Less demand means mining losses, which means mining companies need less equipment. You can see where I am going with this.
His other option is that he doesn't follow through on his threat, and now his base sees he is not the juggernaut he portrays. He will be beaten by the man he calls weak. This will show other countries he is beatable, and will lead to more resistance from international trading partners.
Those who already drank the coolaid will still feel he is their god and saviour, but the moderates and those affected by his policies will realise he might not actually know what he is doing.