Default [Q] US Firmware on EU device

Hello, I know that you can flash the eu firmware on an american moto x to get european languages or so. Is it possible also the opposite thing?
Can I flash a us firmware on an european moto x?
This is because I'd like to root it without unlocking the bootloader, so with the warranty still valid.
I should just downgrade to 4.2.2, but there's no european 4.2.2 since it's shipped with kitkat.

Would I be able to use an american 4.2.2 on an european moto x to downgrade, root and then go back to european 4.4?
thanks