Here's what we'll assume:
- The KMT wins the Chinese Civil War. Mao and his followers are completely defeated The Republic of China then follows the trajectory that many were hoping People's Republic would follow: a few decades of gradually softening authoritarianism, followed by democratic reforms in the 80s and 90s, more or less on the same schedule as the historical Taiwan and South Korea. China stays pro-US in the Cold War, but maintains relatively cordial relations with the USSR. More or less, average out where France and the PRC stood at any given point historically.
- China's economy has grown solidly ever since the end of the civil war. The government has avoided any catastrophes (great leap forward, cultural revolution) costing countless lives and treasure. The economy is more liberalized than the historical PRC's post-Mao economy, but there's still some heavy state-capitalist influences. Fewer giant but unproductive projects designed just to goose economic numbers (ghost cities are the poster child here) but not none. Growth is slower but got started sooner, and while there have been no crazy man made disasters, the economy is more vulnerable to outside economic shocks. We'll say the economy is almost the same size as the US's, but the population is also a little bigger, so per capita isn't too much higher, and growth has been much more sluggish for the past decade or so. Without the one child policy, the population decline has been more gradual, so there is less (but not no) concern about growing old before growing rich.
- There is conflict over the South China Sea, but not as belligerent. Chinese institutions do engage in plenty of espionage, but not as blatantly.
- There are no horrific human rights abuses. Hong Kong was fully integrated without any major difficulty in 97, and Tibet is nominally independent but effectively a condominium between India and China. Autonomous regions really are autonomous.
- Global affairs more or less are recognizable. The Cold War ends on schedule, etc etc. Vietnam and Korea unified under their pro-western governments, but the overall course of the 20th and early 21st centuries is the same.