As an American student I've observed or heard of both international and local students cheating. It really pissed me off when students would come to exams with psychiatrists' notes about a sudden onset of ADHD. Or abuse the sympathy of the teacher to get more time. Crib sheets only occurred in lower level classes where it's hard to observe. At the higher levels it becomes obvious who knows what.

Cheating in school is a cultural thing, far more accepted and normal in for example Eastern Europe than US.

I was a TA at a medium-sized US university 25 years ago. I had a lot of (20 or so) Malaysian students in a class of mine and it was very simple: if they were Chinese Malaysian they worked their butts off. If they were ethnic Malay they were lazy as hell. I caught several of the latter cheating as well.

I've heard similar stories form friends of mine who were also CS TAs.