Which means Clark Kent is an illegal immigrant too. And must have forged documents to gain employment at The Daily Planet. I'm no longer so sure about this Superman guy.....
actually, some retelling of Superman myths in Comics in the last few year have him technically born on earth in Kansas. He was sent to earth in an artificial womb which was standard practice on Krypton and was birthed after it reached Earth.
Actually the whole, "American way" stuff has been going on for a few years in the comic books also, they mentioned the Justice League of America in the Article but a few years ago, the Justice League of America was changed to JLA because they didn't want the word America used because it might offend some.
In the comic the Kents adopt him so my guess is he is naturalized.