A friend and I have been talking this idea over recently, and I wanted some input from the brilliant minds of Alt History. If, for whatever reason, the ROC defeated the PRC in the late forties and remained the internationally-recognized government of China, what would the effects of that be both domestically and internationally? Would the mainland ROC have democratized as early or as thoroughly as Taiwan has? What kind of impact would a rightist and pro-American Chinese government have on the Cold War? Would China's economic development have progressed differently?
I can basically see a very optimistic or very pessimistic set of outcomes, and I don't have the specialized knowledge of the times or conditions to know which was more likely. In international conflicts, the optimistic assessment is that a pro-US Chinese government would mean an early reunification of Korea under the ROK and either an easy Western victory in Vietnam or not much of a war at all, and the much weaker Soviet position leads to an earlier collapse for them as well. The pessimistic assessment is that, with a friendly and war-ready China, the West feels confident enough to fight the Soviets shortly after WW2, probably ending in an eventual US victory but also further destroying Eurasia and leaving Europe in much the same state it was in just after WW1. Which is to say, a very dangerous and chaotic one. Domestically, China would have avoided the catastrophic Great Leap Forward and Cultural Revolution, but beyond that it's hard to say what could have happened economically or socially. Optimistically, China would develop more freely and rapidly between 1950-1980 than it has in OTL without facing many additional challenges; pessimistically you'd end up with an economy that is just as corrupt but even more unequal, with serious potential for unrest in the interior and feeding into Burma-style separatist wars with ethnic minorities. I'm not familiar enough with Taiwan's democratic transition to make any kind of assertion about how it may have gone in a mainland context.