Most of the investors are from US so In my opinion bitcoin will be accepted by USA Soon.
Exactly, Bitcoin is even used on USA exchanges more than the others so why wouldn't they officially accept it in the near future to help cut off illegal/black market usage.
I have seen lots of American investor in lots of ico, so definitely its already used in USA, maybe government were not aware yet or they might thinking of ways to embrace it or eliminate it,we can't tell yet.