I think the assertion is that US has lost core competency at things like steel and cars, so by making it harder to bring in mini-vans from Canada or whatever, they're proposing a magic rebirth of those industries in country. Those are the same competencies we'd need if we wanted to build tanks or battleships or bombers for another assault on Normandy. Which we don't, that was important 80 years ago but not now.

The reality of course is probably more like pandering to steel and auto workers.