You need to setup a US itunes account with a different email address.
You also need a US mailing address - I used the address of the apple store in Florida.
Plus a way to pay for music/apps in dollars - easiest way to do that (if you don't have a US cc) is to get a US itunes gift card from eBay, sellers just email you the serial.
It may let you setup using a promo code - but it might not, I dunno.
Then you can switch stores to the US one on your iphone using the correct email address.