How could Llewelyn run for president? He's not a natural-born citizen of the United States, he's most likely English. Or is there some unspoken loophole still in effect that anyone living in the U.S. who was born before the revolution can be president?
Actually, there is: the requirement is that you either be a natural born citizen or have been a citizen when the Constitution was adopted. I'm not sure this helps Llewellyn, though; I'm pretty sure he isn't quite that old. (For example, this strip suggests that his grandfather was young some time in the 18th century.) Probably he just doesn't care—it would be illegal for him to serve as president, but since he has no intention of winning this isn't an issue.
He definitely doesn't care. Ozy brings up the fact that he's the ruler of Greater Llewellynland and he shrugs it off in his typical fashion.