You can actually get Microsoft to switch the code for you. Just contact support chat on xbox.com and tell them your code isn't working (don't tell them the reason why its not). Give them the code, they will say it is valid and should work, but tell them no. They will give you a support number, and in about a week, they will contact you with a 1400 point code that will work on a US account.
The reason I know this works is I did this before, but to get an American code to work on a Canadian account.
Hope this helps