I agree that in general Peeps ratings are bullshit.  I don't have any hard evidence, but I believe peeps receives payment from books and refuses to be transparent about it.  
I'm also one of Betcoins biggest critics.  
But - Betcoin does accept US players.   I know this to be fact.
Also, I'm pretty sure Nitrogen accepts US players.  I've placed a bunch of bets there as recently as the Superbowl from the US and haven't had any issues.  Perhaps they have a policy that says US players are not allowed, but I don't really care enough to go digging through their T&C.

By the way, do you still think Brady was superbowl MVP?

edit: grammar