Originally Posted by
stephem
Actually, all that matters for using the US site is that you use a credit card with a US billing address, same goes for using the Asia based sites to buy, you must use a C/C with an Asia billing address. I am based in Asia and my WP account has an Asia address, but I use both the Singapore and US websites depending on which has a better deal and better availability (and as I've noted on several threads there are some differences).
They don't even care about your credit card billing address, at least not in Japan. I sometimes use a Japanese Saison with my Japanese address card for booking, and sometimes I use a US AMEX card with my US address card for booking, always on the Japan site.