We are still checking passports and visas at our airports, ports, and at the border. You just don’t walk off a plane and go straight into the US. You also don’t leave without doing the same thing, i.e., go thru passport control. Your passport and visa are scanned.
So as long as they don’t try leaving the country they can overstay as long as they want. The only time we’ll ever catch them is when they’re already trying to leave anyway.
Or if they arrest you after you commit a terrorist attack...
Exactly how does this regime propose to “crack down on” students overstaying their visas, if the only time anybody can check their visas (and how long they are authorized to stay) is when they’re already trying to leave?