Milk issue aside -- actually, let's talk about that one. Canada has accused the US of dumping low-quality milk on the open market, and added an anti-dumping tariff to block it. Trump might be throwing a hissy fit about it, but when
Trump accuses China of dumping low-quality steel on the US, he is
agreeing that Canada is allowed to do this. Saying anything else would be blatant hypocrisy.
Milk issue aside, it seems Trump is mostly pushing for the use of more and more US steel in cars. In alternate timelines, that might make sense. But the US does not make enough steel to suit its own needs -- we are a net importer. Mexico does the same. Canada is about even. That steel has to come from overseas. Even if it didn't, it'd be "stolen" from other industries which would have to import the steel instead. Either way, the cost to the consumer -- because Trump put a tariff on imported steel -- goes up.
Now some of you might say "just open more steel plants in the US, problem solved". Good luck with that. It's not that we're running out, but asking the US iron/steel mining and smelting industry to get the necessary facilities up and running quickly, when Trump and his policies could be out in two years,
while also the price of steel (due to the tariffs) is rising and therefore lowering demand, is asking too much. That, combined with US steel is already too expensive to export, and the tariffs will make it more so.
"Wait, how?"
First of all, if prices for imported steel in the US go up, there's wiggle room for domestic steel to increase as well. There will also be a proportional spike in demand, which will help increase the prices. That, plus if the US buys less imported steel, other countries will happily take the slack -- they didn't put tariffs on it. US steel has nearly no demand in the global market, and that's due to drop.
Anyhow, look at the last two years. Try to find stories about US iron or steel works opening.
Try to find data of iron and steel jobs rising. Despite Trump's actions, promises, and threats, the industry isn't moving on it. We are a capitalistic society, for good or ill. We follow the money.
The steel industry isn't following Trump. They know there's no money there.
And there's a 100% chance Canada knows this. Canada isn't fucking stupid. Neither is Mexico, just to be clear.
With no forseeable strong increase in the US steel market, asking for an increase in US steel in NAFTA cars is asking for the price to increase. Period. Even if such an issue were pushed through, combined with the tariffs,
car sales could drop ten percent as a result. And that's not talking about anything else made of steel, which will be hit by the tariffs (but not in NAFTA that I can see).
So will someone else lose? Yes. It will be US manufacturers, especially auto manufacturers. They will lose.
And they know it, because they aren't stupid either.