I live in Wisconsin and when I was 18 I always went to Michigan to play (well, Upper Michigan). I read up on the subject once, and it sounds like all places in the US are 21+ except a few where the Reservations signed a contract with the goverment before the new rule was established. There are 2 casinos in Wisconsin that are 18+, because the tribes were grandfathered into the new rule. I would assume that would apply to other states as well, unless casinos are a state thing and not a federal thing?
Either way, lots of casinos will let you in at 18 to do bingo! haha