First we excluded Korea from our defense perimeter in 1950, then Lyndon Johnson said he would not send American boys to Vietnam to fight battles that Asian boys should fight, and look what happened. Asia is a big headache for the Army. Sure, we used a lot of helicopters in Vietnam, but that was still nothing like going up against the Soviets. We did it right in Korea by building up the South Korean army so we could go home. If Creighton Abrams had been in charge earlier in Vietnam, Vietnamization would have started earlier, and we would all have been better off.
Strategic bombardment works, it can win wars, and it has.
Nukes were nice but not essential. In Korea, airpower was the war winner. After the Army and Marine Corps had fixed the Chinese, we could plaster them and their supply lines, human waves or not. The problem in Vietnam was that bastard Robert McNamara. When he became secretary of defense, he crippled us with an incremental, politically micromanaged air campaign.