If you Billing account profile at https://billing.microsoft.com shows your address as being US, you aren't able to change this. You can contact support:
How to reach support (FAQ) - http://social.microsoft.com/Forums/en-US/onecareinstallandactivate/thread/30400b52-7f26-4ba0-bc18-17e305329d90
However, my recommendation is that you create a new LiveID and start a new subscription rather than renew. I believe that this will be easier.
If you are purchasing a new subscription and the address form for the purchase information show a US form, you need to change the default language in Internet Explorer to match you current location/language before proceeding.
-steve
Microsoft MVP Windows Live / Windows Live OneCare Forum Moderator