SPOILER WARNING! If you are one of the three people left who regularly reads Superman comics on a monthly basis, you should stop reading immediately.
Seriously: This is your last warning.
Okay. According to Comics Alliance, Superman renounces his U.S. citizenship in a short story in today's Action Comics #900. Here's the relevant panel:
If the right-wing blogs get a hold of this one, there's gonna be hell to pay, especially when somebody realizes that David Goyer, who wrote the story, is also the screenwriter of the upcoming Superman movie directed by Zach Snyder and starring a British person as Superman. So they're neutering America's greatest superhero and turning him into a thug for the United Nations? This could make the Captain America mess look tame in comparison.