It will destroy the economy, entire sectors of commerce will end, and Trump was trying to shut down all trade from the southern boarder entirely his whole last term, no matter how many times his staff told him billions of dollars in trade cross the boarder every single day. If he dosen’t have people in place willing to tell him no. Which he’s getting really good at placing yes men everywhere, then he’ll probably do that as well, and might do it with flights and trains from the south of the US as well. If that happens and he’s dumping billions into depopulating the US by 22mil the US is going see the worst economic disaster in our history by several magnitudes. Maybe enough protesters get organized and strategically block road for long enough to actually slow them down, but with the US military I don’t see that happening.
Fascism is an excellent way to weaken a country. Strong centralized government is very important, but it needs to be an effective government, not one stupid asshole. When its 1000s of technocrats it works very well.