your source for a majority of randomly sampled american teens not being virgins?
I said 18 year olds. Not teens in general.
That said, I don't have a study up my sleeve. Sorry, can't help you there. But I have definitely heard references to such statistics and it is consistent with my own experiences.
In either case, a guy having sex with an 18 year old girl is not ipso facto sexual abuse as seems to be implied here by some.
Maybe she was abused, maybe she wasn't. Saying that she "definitely" was is unsubstantiated.