Is it legal to own cuttlefish in the U.S.A? And if so, where can somebody buy them?

You would probably have better luck at a live fish market, particularly an Asian market than a pet store, seeing how a lot of Asian countries eat cuttlefish (Yay Japan). But as everyone has said, it is hard to keep them alive so it would probably be difficult to keep them alive for sale as food also. Best of luck.