Hmm. I would think that the Soviets would put everything they grab in China into this Manchurian Puppet--IDK if that would match Japan's Manchuko borders or not.
This totally screws Mao; Chiang will win the Civil War, but Sinkiang will probably plunge deeper into the Soviet Sphere of Influence.
Chiang will probably wind up as a Strong US Ally in a situation where the Soviets have grabbed territory.
What this is likely to mean is that in the end of the Cold War, on a similar basis to the fall of Eastern Europe, there is likely to be a fall of Central Asia. The Manchurian government would be imposed on its people and they'd be rid of it. Xinjiang and Mongolia may wind up annexed by China, or they may drift into alliance or neutrality with them, depending on who counterfactually leads China. North Korea is going to be heavily reliant on the People's Republic of Manchuria ITTL, and is likely to get wiped out when Manchuria falls.
Note, also, that this could become a possible WWIII Flashpoint. China post WW2 did have some warlords to consider, Sheng Shicai among them. The Consolidation of China into Nationalist and Communist blocs in this fashion may not be a pretty affair. That said, given the situation at hand, I don't think Chiang was insane enough to attack North, and in OTL, The Soviets managed to avoid a full scale war with the Chinese, despite their border clashes. A Similar situation to Europe applies--Mongolia, Xinjiang, Manchuria and North Korea form a "Harbin Pact", opposite Japan, South Korea, Nationalist China, and other Pro-US Governments in the region.
This doubles the land borders between the Soviet and Western Blocs, and it will have interesting implications for Soviet Power in places like Afghanistan and Iran, but I think this is just going to look like a somewhat remixed OTL; there would be no Vietnam War--perhaps a Cuban War instead?