The problem with this POD is that it all depends on the Pacific plays out since the bomb led to an expedited war, and this not an easy thing to just handwave. Downfall or starvation look to be the only ways for Japan to surrender baring allied invasions in Korea or Manchuria, and what do the Soviets do. If a divided Korea was stipulated regardless of who occupied anything then the possible of a north-south conflict is still there.
Would this still result in MacArthur as head of the Japanese Occupation, or could someone else take over and consequently have to deal it? If it's not MacArthur, then you would at see a counterattack but not an outright invasion since this general won't have either MacArthur's ego and selective interpretation of facts. On the other hand, depending on what the Japanese do in China if then the Chinese Civil War could be altered greatly, that Mao may not win out or at least be kept in longer lasting civil war, that means if China is even weaker than OTL there may not even be a Korean War at all because Mao promising to commit troops even when the PLC was very weak, was the only Stalin gave Kim the green light, Stalin was not going to do the heavy lifting for a war against the U.S.