How do I download an app from the iTunes store when I am living outside of the U.S.?

I recently updated my iPod Touch 4th generation to the iOS 6.1. I did this because many of the apps I wanted to get required the new software. But now that I have it, it won't let me download any apps. Every time I attempt to, a message pops up that says "Your account is not valid for use in the Australian store. You must switch to the U.S. store before purchasing." Well 1) I don't live in Australia, I live in Cambodia. And 2) I went to iTunes and it says I am registered to the U.S. store. Is there any way I can fix this? I never had any problems downloading apps before I updated.