In "Action Comics #900," Superman will renounce his American citizenship, rejecting the international notion that his actions are part of US policy. The shift comes after a personal visit to Iran in support of protesters leads President Ahmadinejad to believe America was declaring war against the government in Tehran. Click Link for article.
But is it that easy?
Renouncing citizenship is not that easy and there is a formal process to do so. Did Superman hire an Immigration Attorney?