As an American living in Germany, I've faced this problem too. A free program called
Hotspot Shield gives me an American IP address. I'm lucky enough to have a US credit card, but gift certificates are also an option. Buy a BoB gift certificate using Google checkout and then purchase the books with the gift certificate. Amazon is the only bookstore so far that has cared about my IP address and they accept the American IP address that Hotspot Shield gives me. It also works for the iTunes store and YouTube. It's not a perfect option, but I've been able to buy all the books I've wanted.