There were many recent instances of even long term US permanent residents being sent to immigration detention centers. Maybe El Salvador gulag is an exaggeration, but being sent to a squalid prison is a very real possibility. Here's one from yesterday [1]. What's preventing them from doing the same to a student?

Also, most people affected by this will not be the son/daughter of the president of a foreign country or a billionaire.

[1] https://www.newsweek.com/green-card-holder-detained-ice-immi...