ITunes store?

When trying to purchase a song from the iTunes store, it said they didn't have it at the US store and would have to switch to the British store. Now I can't switch back to the US store. Any ideas on how to do this?! I've tried everything I know how to do.|||The store you are in is always displayed at the bottom of the page in the iTunes store. To change it, you click on it and select, that should always be available.