I think if Japan is partitioned in WWII between America and Russia instead of dropping the Atomic Bomb, the Communist/Socialist partition of Japan might cause a Vietnam like War and war with the American backed Monarchist state.
What would turn the population to support the Socialist republic that was under Russian occupation would be the memory of the Banning of Literature during around the time of the war, some of the literature that the Right-wing gov.t banned during the Wartime are precursors of the Anime/Manga we have today so we would likely see the Manga and Anime in the Socialist Republic of Japan ITTL, not in the American backed side.
I think Japan, if not bombed in WWII, would be a Vietnam/Germany Analogue during the Cold war.