One of the things I wished I had done over the last 10 years is take a photo of everyone I have seen wearing a Superman T-shirt. I remember seeing a family of four in Malaysia all wearing the same Superman T-shirt around the time Man of Steel was released. The impact of superhero figures in Singapore and other parts of Southeast Asia is also reasonably large. So for instance the Marina Bay Sands resort in Singapore has a huge DC Super Heroes store and cafe complete with superhero ice cream flavors. (And if you wonder what the difference between Superhero and Super Hero might be; therein lays a story of trademark law).
In 2014 the local subway system issued a series of cards with DC characters including Superman.
And Darlie, a popular Asian brand of toothpaste now owned by Colgate-Palmolive, did a similar themed promotion. (If Darlie makes you do a double take look it up and be truly horrified at its past). And of course as Darlie shows commercial western visual representations spread across the world long before superheroes and their ilk.
In short Superman is not simply an American icon, but for those outside the country an icon of America.