iTunes store thinks I live in Canada

Had a similar problem. Here's how you fix it:

Go to iTunes store.
Scroll to the bottom.
Select the appropriate iTunes store for your country.

Not so easy. There is a larger problem at work. I switched to the US store after it thought I was in Canada, iTunes no longer recognizes my U.S. account. I get a message telling me that my ID has never been used with the iTunes store before. That really concerns me since I have some pre-orders in the pipe.

I just had the same problem a few minutes ago. I switched to the US store, and my account, with the credit left in it, had disappeared. However, when I clicked on something like set up an account, I got a screen asking for my user ID and password. When I entered the "old" information I got another screen asking to verify my credit card, address, etc. It was all there and I only had to click on "Done", whereupon my credit reappeared, and I was back in the US store. Weird.
I hope this helps.

"If my response, or any others were helpful or solved the problem, please feel free to check the appropriate box."

My problem is a little different. The iTunes store no longer remembers my account as ever having existed. It tells me the store has never been accessed with the account information I provide.