Thanks for the fdk!
Three things did occur to me after I posted:
1. Instead of giving Superman citizenship, they could have just declared him a resident alien. But I figured they'd want to go ahead and claim him. (And other countries would be free to grant him citizenship too.)
2. I could use the title "Murphy's Law" if that doesn't seem to give things away too early.
3. Superman probably passed the test with flying colors.
