Graeber is dead wrong on this. It wasn't the antiwar movement in the US that caused "Vietnam Syndrome" - being militarily defeated by a nation the US viewed as "inferior" did.
And it also wasn't 9/11 that overcame "Vietnam Syndrome" - the invasion of Panama and the first Gulf War did that.
If the antiwar movement in the US achieved anything, it was to provide the US military with a pretext - ie, somebody to blame - for extracting themselves from a war they had decisively lost.
You need to make those eye-holes bigger.