This
site has a lot of information for you.
Two points; as
Bloss states, some States have the minimum drinking age as 21 and some have lower... the lowest being 18. However, even within States that have lower drinking ages, Counties within that State may have established higher ages.
Additionally, unless your a bona fide
student, you're likely going to find it difficult to obtain a visa for work. You can certainly obtain a tourist visa, but those don't allow work (except under extraordinary circumstances). That's not to say that you couldn't surrepticiously work, but you run the risk of discovery, which can have serious implications. Check the web site above carefully.
Best of luck and welcome to the U.S.!