What if no Korean War?

Yes, it can either help or damage the Korean Republic so it can shorten the Korean War if it exists, I think a Britain/America split could also make America approve a Nuke of China, which could make a relationship between America and China difficult in the future, A nuke of China by America will also make relationship between Britain and US difficult as well as Britain has interests with China.

Yes, but when China opened, they started to move manufacturing there along with the Americans, if China still opened after a Nuke of China by the Americans it is less likely for the Americans to build factories there and perhaps the British and their allies/colonies could build factories there instead creating a monopoly of trade and production by the British and Commonwealth States in China.

Steve is right. If China is hit, there won’t be any ‘opening’ up, let alone movement of factories and concerns. The latter was almost entirely an American factor; a British factories closed full stop in the 1960s-1990s, rather than being moved to China in the 2000s.

As of the Korean War, British interests in China had rapidly evaporated. Again, as Steve says (I end up saying that quite a bit), there is a difference between Hong Kong and, say, the British position in China in the 20s or pre WW1. It is important to remember that all of those previous investments, trade and company links…did not survive through the Sino-Japanese War well.

That…doesn’t make sense. Before any U.S. strike, Red China lacked the ability to cross the Taiwan Strait.

After it, there won’t be sufficient force or support left.

Say if Stalin decided that escalating things in Korea would be more costly than it's worth, he wouldn't allow Kim Il-Sung to attack the South. However, that does not mean Rhee Syng-man wouldn't throw the first punch either, as he might be more ambitious in attempting to reunite the Korean peninsula. If the US tells Rhee to not attack as well, then the Korean peninsula would stabilize for a while, until Stalin's death.

I would also predict that a conflict between the North and the South would play out similarly to what happened in Vietnam, with an underground communist movement in the South causing chaos there (there's also a South Korean Communist Party that existed before 1948, but some of its members had initiated an armed guerrilla struggle before the Korean War broke out). I would suspect that this South Korean Communist guerrilla movement would become an earlier analogue to the Viet Cong, but less organized than its VC counterpart.

Another interesting side effect of a no-Korean War would be post-war Japan's possible economic recovery, which may not happen as a result of them not taking advantage of another country's conflict to reposition itself as a supply hub. Labor disputes would continue, and political violence would be far worse than what has happened in the 1930s. However, sooner or later, there would be a conflict in the Korean peninsula, though of different conditions. I would suspect that a long terrorist campaign on part of the South Korean communists might destabilize the South Korean government long enough for the North to launch its attack.

Overall, a reunified Korea might not be as wealthy as its OTL southern counterpart, because of how devastated it is, but it wouldn't have episodes of famines and malnutrition. However, it would still have gulags and other kinds of concentration camps, which would be a downer.

I might actually plan on adopting this kind of scenario for a map project.

Kyoto was actually considered a plausible target though.