I usually ask people to ponder how history would be different today if the Iron Curtain that fell across Europe were to have included Japan in the 1940's? That was a very likely outcome had we allowed the Soviets to get involved in the War in the Pacific. As it was, the Soviets were trying to play catch-up, having only very recently declaring war on Japan (August 8, 1945, between the bombings).
And imagine if the war extended beyond 1949, when Mao Tse Tung took over China.
The Chinese were going to join in and they were thirsty for revenge, to say the least.
There probably wouldn’t have been a Korean War — Korea would have been given up; the Japanese would have turned on the US if (for example) northern Japan had been occupied by the Soviets, who’d have fanned the militaristic flames, and the US defeated the Japanese almost singlehandedly (their long land war in China was expensive but not a huge source of losses). That might have changed the US attitude toward similar partition deals, for example in Indochina.
The Soviets never wanted Chiang Kai-Shek involved in wartime conferences, and since they played a far larger wartime role in the defeat of the Axis, they got their way; but after victory, their own occupation of Korea, and partial occupation of Japan, they’d probably not have given Mao their unconditional backing, either, preferring to keep two separate regimes in check, one against the other.
Interesting to speculate, regardless. :’)