well, he got honorary citizenship to who knows how many countries in superman 4.. i know, i know.. different canon.. point is he doesn't have to denounce his US citizenship to be honored as a "global citizen".. as a matter of fact, he can be NOT a citizen of any country and still be superman.. he shouldn't be limited just to the "american way".. superman is superman, may he be in the USA, the Philippines, Iran, Iraq, Kuwait, China, North Korea, South Africa, Apokalyps or anywhere.. but not on krypton.. he's just kal-el in krypton..