Moving to the US

forums.xbox.com/.../442533.aspx

you can migrate but not all region locked will work in the us

That's fine, but just to be clear, I'm talking about getting one of these

www.amazon.ca/.../ref=sr_1_79

Not attaching one of those white adapter's to the end of a UK plug. Or is it irrelevant, should I still get a U.S. power brick?

but you must remain signed into live or do a drm transfer to use them

www.xbox.com/drm to start the drm transfer proccess

You can't transfer ms Points or achievements as they are locked to your account and ms points wouldn't work in another account due to region differences

However you can keep the old account and purchase non region specific content still

You don't have to keep I t gold but it should be on your console if you want access to the old content

You can transferr some game saves if the game allows it but generally no But usually achievements are disabled upon transfer

You would need a U.S. power brick.You should not use power converters/adapters of any kind with your console.