If you look at the letters pages in most comic books, you'll find most fans commenting on the stories and the characters, making requests for things they'd like to see, or criticising things they didn't like. And Captain America's "Let's Rap With Cap" letters page was largely the same - except a lot of letters also talked about important issues of the day, including discussions on what it meant to be an American and a patriot. When the Cap comics really hit their stride in the late 60s, there was a lot of political turmoil. The Vietnam War, the Civil Rights Movement, Watergate, the counterculture, and countless other things. And the comics, particularly under writer Steve Englehart, reflected this. The readers responded in kind. Marvel received letters from all across the ideological spectrum, discussing important issues of the day and even responding to each other. In regards to Steve Rogers' political stance, Roger Stern wrote a lengthy response in Captain America #247 to a fan who felt Cap was a Reagan conservative: "Cap is not quite the rock-ribbed conservative you imagine him to be. As a matter of fact, hes probably about as dead center in the political spectrum as one can get... If anything, Steve Rogers probably grew up as a New Deal liberal." Hardly seems like the kind of discussion that would appear in a comic book free of politics.
Percival Constantine is the author of several novels and short stories, including the Vanguard superhero series, and regularly writes and comments on movies, comics, and other pop culture. More information can be found at his website, PercivalConstantine.com