Without JFK, LBJ, and Vietnam the left would not have had the chaos and stirred up masses to work with to break everything.
As far as winning the war “easily”, Red China, Russia, and North Korea may have caused more issues than you are thinking about if you remember the world situation back then.
Nope, by then the USSR and China had fallen out and hated each other, and neither wanted to fight with the US. The “we can’t use our full strength because we don’t want to risk provoking Russia and China” is precisely the kind of mentality the fifth columnist propagandists promulgated in the US as they were instructed to do by their Soviet masters.
It was a three pronged approach, 1, was to question the legitimacy of US involvement, including the whole anti-war hippies movement.2. Hamstring the effectiveness of the US military by constantly using nuclear war as the bogeyman to scare the politicians from using the force necessary to win. 3, demoralize the population into believing that victory was not possible and thus stop supporting the effort.
It worked.