It is no wonder that reports that Superman is considering renouncing his US citizenship are causing consternation across the Atlantic. He might have been born on Krypton, but Superman, more than any other superhero, has always exuded Americana. Were he not invulnerable, the man of steel would probably bleed red, white and blue.
So for Superman to ditch his formal allegiance to the Stars and Stripes is like Spider-man developing arachnophobia, or Batman announcing that he's sick of policing dark alleyways, or the Incredible Hulk taking anger management classes. It would be a gross deviation from comic history, an intolerable challenge to the traditional order. But Superman better watch out for the domestic political backlash too.
US conservatives are in a less than tolerant mood. Those who are not with them are deemed to be against them. Indeed, it will probably be only a short while before Donald Trump demands proof that Superman was really brought up in Kansas.