There is a third party application called "Market Enabler", which spoofs your location information so Google thinks you are in a different country. However it isn't currently working because of the latest update to PlayStore and will need to be patched.
Here's a link to it - but remember it isn't working right now. Keep checking the page for an update.
It also requires root access, so if your phone isn't rooted or you have no intention of rooting, don't even bother with it.
I don't see why you would want to change it anyway, the US appstore has the most selection.
For example here in Canada, we have books, magazines, movies, tv shows, but not music. This remains to be a feature only found in the US.