OOC: I think I once tried to do this in WI form but I couldn't get any attention. I think it's an aweasomely quirky idea, so it's perfect for a DBWI.
IC:
As we all know, the Union of Soviet Socialist Republics was born out of the Twin Struggles of the nations of Russia and Japan. By the late 1910s, socialist revolutionary movements were spreading all throughout the world. However, only in these two cases were they successful.
Without wanting to ignore all the other Soviet republics, I'm well aware that the Union stretches from Finland to Formosa, it was allways Russian and Japan that headed the worker's state in a kind of bicephalous leadership.
But what if that hadn't been the case? What if the revolution had succeeded only in one of these two countries? What would a fully Russian-dominated or fully Japanese-dominated Soviet Union look like?
Of the top of my head, I'd say that a Russian SU would probably encompass all of the central Asian republics, as well as the Finnish, Ukrainian, Moldovan and Byelorussian SSRs. If WWII still happens and they still find themselves at war with Axis China, they can probably take Xianjing as well, as our Soviet Union did.
A Japanese USSR would likely be composed of the Japanese, Korean, Manchurian and Formosan SSRs, and I wonder what they could achieve in a war against China...
One thing that is certain, though, is that both of these smaller Soviet Unions would be much less of a world power than the USSR that we know. Maybe it would collapse during the 20th century, leading to a world of absolute American hegemony.
Now that the tense atmosphere of the Cold War is finally easing, with the governments of both countries joining together in a common front to fight terrorism, and with Soviet animation and other kinds of pop-culture becoming surprisingly popular in the west, it is certainly an interesting time to be asking these questions.