I'm guessing Mutally Assured Destruction wiped them under the mat.
I'd like to see a future game where a resurgent Chinese faction appears, maybe taking the place of the Enclave. Imagine they built up a war machine in the 200 years since and start invading America?
A friend of mine suggested something similar to that,but I would think that like in a America,the bombs made all the pre-war ideologies meaningless and many Chinese would even forget about America's existence. Just like with Moria Brown's terminal, where she wonders if China was fictional.
After thinking about it since posting this topic, I relized that the best chance for a significant Chinese presence in America would be the Shi in San Francisco. They were well on their way to developing their own Vertibirds,they had their own power armor, and even developed a plant that absorbs radiation out of its surroundings,plus their Chinese heretiege was intact.