Billing Address in a Different Country

I’m currently working in Japan but my billing address for my credit card is back in the US. I needed to get apps only available in the Japanese App Store so I changed my region to Japan, but now I can’t re-enter my card because it won’t let me put an American address. Is there a way to add it? Additionally, why does the App Store cancel subscriptions if you change region?!? Now I can’t re-subscribe to my old services because I can’t add my card!!