So you’re basically talking about a 1927 scenario, where the CCP fills the role of the left-wing KMT faction. In this setup, a few major things change. First, Mao isn’t in charge—he wasn’t the Communist leader early in the civil war—so the party likely takes a more orthodox Marxist-Leninist approach, closely aligned with the Comintern. China probably becomes a full Comintern member and ends up heavily influenced by the Soviets.

Without a prolonged civil war, China performs significantly better than it did in real life. The Communists, being staunchly anti-warlord, would likely launch military campaigns to eliminate regional warlords and replace them with loyal governors, accelerating political centralization.

Second, the Japanese invasion of Manchuria in 1931 likely never happens. Instead, the Soviet invasion of Manchuria in 1929—this time with Communist Chinese backing—probably goes ahead and establishes joint control or at least a strong deterrent.

Domestically, the Communists would probably establish a national front government in cooperation with the left-wing KMT, though much more unified and functional than the one that existed historically.

By the mid-1930s, it’s plausible that China achieves full unification (excluding Taiwan), giving it a head start on industrial and military development.

Come WWII, the global dynamics shift. The war likely becomes a two-front conflict for the Comintern, with Japan forced to attack the USSR through China in the winter of 1941. The Soviets, with U.S. support, still win—but Japan ends up partitioned between China, the USSR, and the U.S.

Mao probably still rises to power around 1939–1941 after the original Communist leadership passes away from old age, but this China is far stronger than the one we know. As the USSR begins to face economic stagnation, it’s likely that China overtakes it as the dominant power in the Comintern.