There is one of those things where it would probably be better to have a more specific POD.
The main one is whether you posit the Communists taking over ALL of China (even Taiwan and Hong Kong?) or just most of it, more than they had, while there is still a US supported non-Communist government based in the South. Presumably the Communists get Beijing in this scenario but do they still have Nanjing?
With a really different Chinese regime, one that is Communist, now you affect not just Korea, but Mongolia, Tibet, Hong Kong, Macao, Vietnam, and Burma, but this depends on whether our "People's Republic of China", I think that is what they were going to call it, holds all the southern provinces.
Also without being beaten again -remember they also got beat pretty badly in the 1930s- by the nationalists, I suspect you would have had a saner Communist regime and someone different than Mao would have been in charge.
Presumably cooperation between the Nationalists and the US doesn't happen in this timeline or is less effective somehow, and that has butterflies. Does this extend to the war against Japan and are the Japanese stronger in China than in OTL in 1944?