First, I'm still going to call it NAFTA. Why? The only reason Trump did this was to have a re-named trade agreement. He has all but admitted it. The point was to re-name it. He has trash-talked NAFTA without knowing a thing about it, so he had to have something with a different name, and has made comments about bad connotations with the name, but there are no connotations with "NAFTA." Nobody knows a thing about it, and nobody thinks about it. This is just Trumpian bluster.
If NAFTA had been the catastrophe that Trump always insisted, he wouldn't have agreed to a framework that was essentially the same, but with some minor tweaks. This was primarily a re-naming exercise. So, let's just keep calling it NAFTA, to bug Trump. It's mostly NAFTA anyway.
But...
Trump did get some concessions, mostly on dairy. Tariffs got concessions. Yes. The US is in a stronger position in terms of trade with Canada after those tariffs than before. And I, the Trump-hating-est Trump-despiser of them all, give you permission to admit that. I, an economically-trained political scientist who bashes mercantilism, am telling you that it is OK to admit that tariffs got concessions from Canada on the small issue of dairy trade within NAFTA.
Always acknowledge reality.
Does it follow from this that trade wars are good, and/or easy to win? No. What's different about China? Notice that things are going a little differently with that trade war. Tariffs just keep getting ramped up there, and we aren't any closer to a deal. A few things. First, and I'm not the only one to point this out, they can wait Trump out. Trump'll be gone, the next president will drop this idiotic bullshit if Donny doesn't, and Xi wins. Trump wants to be President-for-life, but Xi is. Second, NAFTA was already in place. Third, the US and Canada are allies, with Canada as junior partner, geographically and economically in a unique position. Press too hard for too much, and Canada couldn't give, but some dairy stuff? Sure. Why not? Let Trump have a little something, and move on because the US really is the dominant player in that specific relationship, if the president just decides to be the douchebag-iest douchebag in the history of douchebags.
But, and of course, there's a but...
And as the saying goes, "everything before the 'but' is irrelevant...."
The US and Canada are still going to interact with each other, and the relationship changed. Trump declared Canada a threat to US national security. For total bullshit reasons, to play stupid, narcissistic, mercantilist games, because he is an idiot child. As a general rule, Canadians are polite (yeah, there I go, stereotyping, but fuck it...), and they could decide that this is just a Trump thing, but actions have consequences, and just because the US got some minor concessions without giving this time doesn't mean there won't be consequences from a stupidly and needlessly poisoned relationship. Calling one of your closest allies a threat to national security for stupid, bullshit games? You might win that round, but international relations are repeated interactions, and what happens now?
Does Canada make more effort to trade with other countries? The simplest reaction for Canada is to decide, rationally and intelligently, that the US cannot be trusted, and start diversifying its trade relationships more. Who loses? We do. Invisibly. Perhaps slowly and gradually, but the right move for Canada is to ween itself away from the US so that this cannot happen again. Given its geographic location, that's difficult, but the alternative is worse. The US simply cannot be trusted.
Evidence? Donald fuckin' Trump. It was minor this time, but the fact that it happened demonstrates this country simply cannot be trusted to abide by its trade agreements. Too high a risk of an idiot demagogue who can't do math.
So, yes, Trump got something by invoking tariffs. Does that validate mercantilism? No.