Earlier quoted context omitted.
They can (try and) transfer to another college / university. But, I suspect, if suddenly all international students transferred to MIT, the administration would simply do the same to MIT. So it would become one big game of whack-a-mole, and the smaller players would just bend over to the rules. International students are cash cows for some institutions. They wouldn't dare to have that cow put down.
The Trump administration is not targeting the students, they're targeting Harvard. The students are collateral damage. So transferring to another college will be fine as long as they pick one that has already kowtowed to Trump. And have never posted to social media or taken any action that could be construed as opposition to the policies of the Dear Leader.
The Trump Administration is targeting Harvard, foreign students (and foreigners, especially non-White foreigners, generally), free speech, due process, limited government, and constraints on executive power, and a whole bunch of other things simultaneously.
"It's this, not that" is the wrong mental model. It is more like, everything, everywhere, all at once.