Unfortunately, Dumbledore is British and Optimus Prime is from outer space. Neither is a natural born/manufactured citizen.
Dumbledore is a wizard, he could probably just cast a spell that would give him the correct papers or hypnotize everyone to believe that he is as american as Captain America despite his accent and suspiciously long (muslim like) beard.
And Optimus is a giant killer robot with built in weaponry.
...I don't think anyone would argue.