As an American emigrant: the red cups are real, but not limited to house parties; alcohol is a lot less accessible, so the party would be more likely to have four different kinds of liqueur from peoples parents or three handles of paint cleaner; getting the cops called on an underage party is serious. Like, potentially lose your job and home serious, even if you were gone for the weekend.

Oh no. Wait until he finds out what frat parties really look like

It is untrue. You can go to any highschool and find giant parties happening several times a year. It happens at multiple schools, kids travel to the next school over, and they will typical be 100s of kids at these things.

Maybe it's changing with gen z but the overwhelming majority of American high schoolers in the 90s and 00s were having drinks from time to time and party.