Yeah, the entirety of the US war on Vietnam has gotten memory holed into being this big, unpopular mistake when the truth was that it was fairly popular at first
Lots of volunteers, lots of pro-war sentiment
Took the war dragging on for several years for opinion to start changing, but the two big nails in the coffin were the Tet Offensive and the release of the Pentagon Papers
The combination of the supposedly defeated North Vietnamese striking back with a vengeance and the public finding out that the Gulf of Tonkin incident was a farce was what finally broke the majority of public support
Atrocities like the My Lai Massacre and Tiger Force didn't do much to get people turned off, and neither did the Kent State shooting
Yeah my grandparents still talk nostalgically about the good old days when the government knew how to deal with communists. How unfair everyone was to Nixon.
I remember some of my earliest political arguments online discussing the subject of don't ask don't tell and pushing back against the notion that it should have been left to the joint chiefs or some shit. Trying to point out that we have (allegedly) a military beholden to a civilian government back then much like today will get you more than a few "Tell that to the kids at Kent state". There is a very deep sickness that runs through this godforsaken country.
They know of Tiamen square. I wouldn't say they know about it.
They just see a guy in front of a tank and then go "oooo, brave, standing up to the CeceePee."
But seriously, like maybe to an extent. At least in so far as the pigs aren't just going in there to shoot and kill protestors. Doesn't mean they won't brutalize protestors in other ways of course. And I honestly wonder how many Americans even know about Kent State. Even in my relatively good education I think Kent State was mentioned once or twice from elementary school through college.