The fact that you can't change your address on the Square Enix website or through support has nothing to do with the payment processor, laws or taxes. It's a stupid choice made by SE.

Also, if other companies can take money from people who physically move countries then there is no reason SE couldn't as well. Simple as that. This is the only gaming company that expects you to delete your account if you move, it's completely absurd. People need to stop excusing bad service.