First, if you are talking about standing militaries, between the U.S., South Korea, and Taiwan, they mass roughly 3 million, compared to the Chinese 3 million. If you go to reserves, we have over 3 million more, while the Chinese have another 3 million. Now you have to add the North Koreans to that, but their military is also in s sorry state. Plus, they would be overwhelmed quickly, limiting mobilization time. Seato forces would probably be slightly outnumbered, but they are much more advanced, better trained and with significantly more powerful air and sea power.
Second, if there is more of a build up, we would actually be in more of an advatage. The Chinese fielding a 200 million man army, don’t make me laugh, Yanny. How would they feed them? HOw would they arm them? How would they make up for the lost productiveity? Less farmers, less workers. How would they train them?
Seato could train more troops faster who are better trained and armed. With our massively superior air force, we could waste the inferior troops they can mobilize.
South Korea could take care of North Korea by itself. The economies and population of Seato can mobilize/support 10s of millions of troops.
One major obstacle is China’s nuclear arsenal. However, between all four countries’ intelligence agencies and the ABMD system and airpower we are developing (which is already being deployed/developed in Seato countries) we can neutralize missiles on the ground/interrupt chain of command to launch them/take them out in the air.
Finally, not everyone in China loves the government, We can contact anti-government groups and use them to our advantage.