Your Xbox, even when it's hooked into the Xbox Live interface, only knows the information that you input. When you fill out your account information--including your name, address, and billing information--you're telling the Xbox where it's located. This information also is given out in your gamer profile. To make your Xbox think it's in the US, even when it isn't, you should change this information to reflect a U.S. address and phone number.
Sign into your Xbox Live account. Go to xbox.com/en-us/changelocale.htm. Click on United States--it's the last country listed--to make your Live Account access default to the United States.
Go to xbox.com/accounts and click on "Account Summary." Select "Edit" to change your address and phone number in the Xbox Live records. You should choose an address and phone number that reflect a U.S. location.
Turn on your Xbox. Wait until the dashboard is loaded. Click on the "My Xbox" section and use the A button to select it.
Select "Edit Profile." Select "Location."
Update your location to reflect the changes you made on your Xbox Live account. Press the "A" button to save your new location to your profile.