“They can’t legally do that!” They can absolutely do that, and then the legal/illegal part is up to you to make a case over from wherever they imprison/deport you to This has already happened to people in the past, the issue here is mostly one of scale

The US Government, notorious for letting the law get in their way from committing atrocities /j

Them: You can’t deport me! I’m an American! See, here’s my passport! Police: (takes passport, throws it away) Shut up and get in the van.

We’ve already seen the “let’s just do it anyway and then endlessly stonewall any case anyone tries to bring” approach from Trump regarding everything else and to date it’s worked pretty well, why the fuck WOULDN’T he employ it when it comes to deporting citizens?

I do remember more than one story of people of Hispanic descent with hard documentation of their birth in the US being held in detention centers for months during the Trump administration, so it's absolutely happening already.

It feels like we’ve memory holed the first Trump administration in which people legally in the United States were in fact deported and the admin was actively trying to denaturalize citizens.