Is hookah legal in the US?

As ever, this depends on the circumstances of intent. It is not illegal to own/carry a Baseball bat, but it is an offense to threaten someone with the said bat.

There is no specific law that labels a hookah as drug paraphernalia, but it can be considered as such in a court of law.

While possessing a hookah in itself in not illegal. Possessing a hookah with any drugs or drug residue in it would make it drug paraphernalia.