Let us, for the moment, ignore the FoF and people are are simply against gambling. They are like teetotalers that think we should return to alcohol prohibition -- it is no use trying to reason with them.

The US government is generally really concerned with just a few things:

1. Do they get tax revenue?
2. Criminal activity (meaning crimes comitted by someone besides the US government)
3. Does a lobby that gives them lots of bribes, uh, I mean donations, have an opinion?

For (1) and (2) you simply need US law to apply. A simple solution would be to require the online casinos to have US based subsidiaries that the US government can sanction in the event that they are unhappy with a poker site. The US subsidiaries could generate profit (and tax revenue) that is some how related to US players (e.g. US player generated rake) and they could also report US player winnings to the IRS, along with cooperating with FBI investigations into money laundering and other organized crime fraud.

The real bogey man here for the US government is not gambling (if it was then brick and mortar casinos would not be springing up like weeds) the bogeyman is the inability of the US government to exert control over the internet casinos.

We could satisfy both parties by giving the US some what it really wants (some regulatory say so and tax revenue) and the players and online poker rooms what they want (legal in the US online poker). I'm sure PokerStars and FullTilt could manage setting up US subsidiaries in order to have access to US poker players.

That's called HR 2046, the Internet Gambling Regulation and Enforcement Act.

This ignores a more basic question: why didn't the online casinos set up shop in the United States in the first place? The answer is because in any state they set up their physical shop, they would be shut down as an illegal gambling operation under state law.