Easily defeated? So what happened in Vietnam than, ya don't go blaming on "liberal" media on this? In Korea McArthur was losing the war with too many American lives from far away land (very unpopular to the American public) and he was desperate to end it with a nuke. But Truman was fearful of a retaliation from the Soviet Union that's why he thought better. Regime changer doesn't like it whenever they lost to "Communists".
What happened in Vietnam? The generals violated one of the most basic rules in war, they did not move forward and take enemy territory. They kept troops at their bases in South Vietnam and flew out in helicopters to patrol and engage the enemy which set them up for ambushes. If they would have moved north constantly and took territory they would have won.
In Korea McArthur was losing the war? He was winning the war against North Korea until China invaded. Even though the US had better weapons the Chinese were smarter than the Americans. The Chinese hid during the daytime (NK is mountainous whereas SK is not nearly as much) when the US fighters were over head then they moved and attacked at night. They pushed the American troops back to about the 38th parallel but it is unlikely that they would have been able to take all of Korea because their supply lines would be too long and exposed to US fighters.
Truman was fearful of the Soviet Union? I have never read that. If he was afraid of the Soviet Union then why would he get involved at all? Why not just let them have all of Korea?