At this point - like many other things in the US - it's up to each individual state, based on current interpretation of the Wire Act and other relevant laws.To my way of thinking, a full re-instatement of above board online poker in the US is the one and only thing that will bring back some of the glory days to poker rooms across America.
I think six US states currently have legal online options, and IIRC some states have cross-state compacts that allow players from one state to play with those from another (bigger player pools are good). I don't play online beyond local Mavens games, so I'm not up to date on the current state of things.