Earlier quoted context omitted.
As far as I'm concerned, Edward Snowden is an American hero... He's a hero. Putting the word American in there is very, well, American. The NSA has done a lot worse by foreigners than Americans.
I think it's clear he meant that he is a hero to/for Americans, without anything further being implied in the positive or negative. There's absolutely nothing unique about inserting the nationality of a hero that relates to Americans. I see it done regularly by citizens of other countries. In my observation, national pride is nearly universal.
In my observation, it might be universal, but its degree varies greatly, with americans on the high end of the scale.
Nobody would say "a Greek hero".