Deathclaws are mutated Jackson's Chameleons, they are not indigenous to China (or Asia, they are from Africa).
(Not even going to address Super Mutants).
Deathclaws are pre-war mutated Jackson Chameleons. USA made Deathclaws, Wanamingo and mole rats to cause alot of damage in China, they were all made before the great war.
I picture China as a land with massive swarms of highly radioactive glowing Ghouls. All of central Asia for that matter, swarms that came out of India as well. My guess would be China's population by time of the great war would be close to Two Billion. USA and other countries like the USSR would have used enough nukes to kill as many as they could. Reason why China has such a high population is because in the 1950s the thinking was America and USSR would only have a few thousand survivors of a nuclear while they would have a millions. Still knowing this China would have been hit at least a dozen times over what was needed to kill off their major cities to stop that theory from coming true. Anyone left alive would become a ghoul.
American troops occupied much of China which means there is a high chance America managed to capture many of China's land based missle sites. Still would not save them from being nuked.