I think they get applied with the intent of being rapidly removed the moment Mexico and Canada give Trump some concession he can declare victory with.
How Mexico and Canada behave will determine whether this turns into a quick Trump PR victory, or something nasty and drawn out.
If Trump turns to financial penalties like bank sanctions or OFAC regulations, it will shake the foundations of the entire world's finances. I don't think it will go there, but I don't rule it out either.
I agree that was the intent, but Trumps rhetoric escalated everything. If he had talked about wanting to renegotiate trade deals because mexico and china were breaking the spirit of the agreement with chinese company pass throughs, or he wanted more border security from canada in exchange for better trade terms no one would have cared or paid much attention, trade negotiations always happen. But he started to talk about turning canada into the 51st state if they didn't bend to what he wanted and he was going to use economic means to take over the country, incredibly stupid shit like that, and now it's turned into a matter of national pride that we won't be bullied or forced to submit to the US.
If Trump turns to such drastic measures like bank sanctions or OFAC regulations it has escalated to the point where we have been embargoing potash, the american food supply has collapsed and we're probably very close to an actual war. I would expect that Canada would be leaning hard on allies such as the EU to support in economic pressure on the US, and I don't think the US citizens, who are already not super into this (go see r/conservative the most pro-trump forum i will view is really not in favor of this), would support something like that for more than a few seconds. With an election in 2026 republicans would get completely wiped out.