But in the last new episode of Smallville, Clark accuses his mother of forging his adoption papers and an earlier episode, some seasons back, had a bogus adoption agency involved.

I suspect we can probably go with Clark being a citizen simply because 1966 was simpler times. He was a foundling, legally adopted.


Big Apricot Superman Movieverse
The World of Lois & Clark
Richard White to Lois Lane: Lois, Superman is afraid of you. What chance has Clark Kent got? - After the Storm