Maybe the restrictions differ from state to state, but I think that first of all, you should be guided by what is written in the ToS on Betfury's website. It is clearly written there that Betfury doesn't allow the opening or use of accounts for clients residing in certain jurisdictions, including the United States.
That's common for 99.99% of online casinos licensed in Curacao and perhaps even other jurisdictions. I haven't checked Betfury's ToS in regards to allowing US players to gamble there. Since philipma1957 is from The States and he says he bets on Betfury, I assumed they don't mind it. I hope, at least, that he cleared it up with their support so he doesn't wake up with a nasty surprise one morning and a blocked account.