My partner had 10k confiscated by them.
Nitrogen Sports has an ambiguous rule: you warranty that it's legal for you to bet online where you are. It's not legal to bet online at Nitrogen in the US or in Costa Rica. They used this rule to take 10k out of an account after the player was active for 4 months. So they know where a player is playing, and selectively enforce it if they are sure you are a long-term winner.
This same rule lets them confiscate any balance from a US player. When a book starts confiscating balances on ambiguous rules, there are much worse problems going on. If you play and win here consistently, I wouldn't expect to be paid my winnings.
FYI I'm Elihu Feustel, same as in the twitter thread on this topic:
https://twitter.com/d_feustel/status/1521178127036305415Hope nitrogensports representative can officially clear out whether US users are welcome or not (for now this looks banning a profitable player and holding their $)