Here's a little article from Comic Book Resources about Superman, Batman, and Wonder Woman. I'm not really sure what the overall point of the article is, but it begins its conclusion:
So Superman becomes this bland, blank slate upon which a wide range of philosophies can be projected.
Then here's something from The Daily Caller. It tackles the accusation that Superman is an illegal immigrant.
There are some problems with the Supeheroes who pose for pictures with tourists in Hollywood.