If Asia had been left in the hands of the Japanese, it probably would have been local movements that eventually drove them out. These various groups would be untitled only around repelling the Japanese, and after that task had been accomplished would have no reason to cooperate with one another. Likely China would have made a grab at Korea in the Japanese exodus or shortly thereafter. The result is uncertain, but given that Korea divided itself in the actual timeline, it likely would have done so again in realistic alternative timelines as well.