|(Prime Vault-Co Meme)|
China is not stupid. They know the only thing that stands between them and global hegemony is Kwanstainia, a degenerate nation of crotch-grabbers with a lot of powerful technology still left behind from the era they had actual people living there.
A couple launch keys and the Chinese know that the 'Stain could do them a lot of damage with very little effort, despite being too dumb to even know how most of their weapons work. They have prepared accordingly.
The Chinese are planning to survive a first strike and retaliate in kind. When the smoke clears in China, the population will emerge from the sanctuary of their substantial civil defense program and resume their lives. In the United States the smoke clearing will consist of the people who used to live there before they were vaporized.