In the UK it would be forgery - a forged instrument is "any document", and for it to be forgery they have to use it to "induce someone to accept it as genuine, and by reason of so accepting it to do or not to do some act to his own or any other person’s prejudice"

I seriously doubt that the US is going have to have less strict laws regarding forged documents. Just because you think it isn't illegal doesn't mean it actually is.