You can believe whatever history the Chinese government spins, but China's takeover of Tibet was a military invasion of a country that believed it was independent. Sure, China had one time ruled Tibet, but the same could be said of Vietnam, the only difference was that Vietnam was no longer under Chinese rule further back in history than Tibet. WhenThe CIA did propose Tibet to join the anti-Communist alliance in 1950, which was turned down by the Tibetan government because Tibet trusted the west even less than China, which it thought was Buddhist. When the ruling regime discovered that the CCP was against religion, it was already too late as they had already accepted the 17 points agreement, which accepted Chinese sovereignty. So yes, in that sense, Tibet was not in fact taken by the PRC through military force (aka invasion), they only rebelled after China tried to impose socialist reforms in Kham, which threatened the Tibetan religious order in 1957. Nationalist narratives today would like to see everything as invasions of one nation over another, except nations are forged, not pre-existing, and are often secondary to other forms of identity, such as religion.
The Communist did not conquer all of Korea as they tried to do, and a non Communist South Korea was preserved, despite Communist attempts to destroy it, so US objectives were achieved. China's client state North Korea is a basket case, while US client South Korea is a resounding economic success, the difference between China and the US. US was tired of war, after having fought on 2 fronts in WW2, while the Chinese were as interested in fighting each other as driving the Japanese out.China considered it a victory because China achieved its pre-war objectives. North Korea's performance before that are largely only of interest to the Koreans.
The US claimed a draw against the communist forces in general, but lost against China itself in the sense that China pushed the UN forces out of North Korea, with the frontier near the Yalu river right before China entered, and back at the 38th parallel after the war ended.
The Chinese were not even coming close to driving the Japanese out of China, and typical Chinese lies to the contrary, the Chinese never came close to defeating the Japanese or driving them out of Manchuria, despite the aid the US gave to China. The Japanese would still be controlling Manchuria to this day if it had been left up to the Chinese. In a decade of fighting, the Chinese had made no progress in driving out the Japanese from Manchuria or the rest of China.The Japanese did not decisively annihilate resistance, they were stopped in their track in the 3 battles of Changsha and lost their momentum, which was why they attacked the other allies in the first place. As for Japan holding on to the rest of China, you are underestimating the growth of Communist forces throughout the war, growing from merely 50,000 in 1937 to 900,000 by 1945. The CCP defeated the Nationalists in just 4 years, something the Japanese couldn't do in 8 and defeated McArthur himself, something the Japanese also failed to do.