I recently dug out a dvd copy of The bridge at Remagen (1969) off my shelf and when I asked about it online, many people who saw it when it was in theatres said it was really a Vietnam war protest.

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Don't know that movie myself, but quite possible.

MASH (technically a Korean War movie/show, but yeah) definitely was a Vietnam protest. The other big one that comes to mind is oddly Kelly's Heroes, which was one of the first big upends - the square-jawed American heroes replaced with a gang of treasure hunters, complete with a tanker straight out of Woodstock. Not a protest per se, but definitely a shift in focus from jingoism to cynicism.