Huh? I thought it was agreed on many other threads that all you have to do is change the address of your Kindle to a US one. No proxies, no gift cards. At the very worst, Amazon will send you a 'warning' email when you buy things. As an added bonus, the books are usually cheaper!
Think of it - Amazon will do the minimum amount publishers require to protect their agreements, since Amazon still gets the sale in the end.