If you are trying to change the country/region of your app store (apple store) to say the United States App store you may have to tweak some of the address in the billing part. In this area you can simply give it a dummy address, phone, etc. When I say dummy i mean fake (not your real info) but you may need to input a state and city that match a particular zip code and area code. Area code is the first three digits of that city then the rest of the number you can made up.
You can find a city, state, zip code, and area codes here: http://zipatlas.com/
If you need help please comment below. Any subs is greatly appreciated as well.