I apologize for the trite and stereotypical answer, and I don’t mean to offend, but you said what it conjures, so I can’t very well make something up; I think about a big muscular guy with a buzz cut, sunglasses and a shitload of firearms, who fights for the best interest of America.
All I know is movies. And even then, the idea my mind conjures is laughable today; what I describe was only awesome in the nineties.
If I google ’‘Real American Hero’’, I bet it’s gonna give me something like that, though.
Otherwise, I don’t know. Maybe a real American hero is someone who did something for their country’s best interest, as described by the constitution, and despite being opposed in their idea, still made a difference for the better of what America aspires to.
EDIT- I Googled it, and it’s just what I thought, eh.