There have been a couple threads on music and the American military during the Vietnam War and the way music is used to evoke the Vietnam War in film/video games/etc.
And my answer in this thread: "Did US Military in Vietnam really listen to "Creedence Clearwater Revival"? What kind of music did they listen to?". OP asked about the anti-war connotations of the songs associated with the war in media, like "Fortunate Son", and that's really at the crux of the question imo. So many songs have become indelibly associated with the Vietnam War in film, either because they were used in memorable ways (the use of Wagner and the Doors in Apocalypse Now) or because their political/subcultural associations play into a particular narrative of the war, emphasizing one aspect or another (drug use and the counterculture, misplaced jingoism, ironic naivete) rather than reflecting the more banal variety of music people were listening to. At the same time, people really were listening to a lot of music over the course of the conflict; Americans in Vietnam were maintaining the personal tastes they were used to back home in the US, as well as being exposed to new music that resonated with their current situation, whether earnestly or ironically.