Not so sure about that. In the beginning, yes, but if, IF, interstate pacts arise, then international pacts can't be very far behind. Plus nothing I have read so far prevents any state who decides to enact laws from pooling their players into an existing international player pool. So just like one of them southern states created walls preventing international play by residents of that state, a state could also create openings to any site it deemed fit.
Getting states to agree to interstate pacts is a much harder task then it sounds. What reason does a state like Nevada, which will have highest player count (in beginning), have for partnering with South Dakota? It doesn't. Yeah, some states like California, Nevada, Florida, New York, big population states could possibly work together, but that would just monopolize
poker sites to the big states and anyone living in a smaller populous state = no good online sites.
The problem is the politicians/leaders don't care about the quality of play, player counts, etc. only about money (which i'm sure you know). By letting in other states/international player pools, it means their slice of the pie becomes smaller. Plus, all the red tape that comes along with having states sharing revenue is far too much for our pathetic government to handle.