If restricted to the photo category, it's certainly up there... the V-day sailor-nurse kiss in Times Square also comes to mind.
If the genre is expanded to all American Icons, I'd think the Statue of Liberty takes the cake.
“Dewey Defeats Truman” would be in the top ten, too.
Let’s see.. (not all of these are parodied, but are at least famous):
Astronaut on the moon saluting the flag would be up there.
There’s that Vietnamese guy shooting a prisoner with a pistol.
Little naked Vietnamese girl (napalm attack victim)
The soldier in the Spanish Civil War that looks like he just got shot in the back
Marilyn Monroe over the wind grate
... oh — and:
The Depression-era mother clutching her kids