Hi Sammi,
Its not jusy whether you drink or not its possible you wont even be allowed in some places even if not drinking, they can be very strict. That will mean you not mixing with others, possibly not able to eat at the same places and I feel any holiday is about seeing great places and meeting new people (making friends).
Don't let me put you off though America is a fantastic place to visit I'm just suggesting you may be best to do it after you reach 21.
Hope you have a great holiday whatever you decide.
Mick