Something many forget is that the US has a better demographic situation than China has, and it is all of China's own making with the one-child policy etc. As people age, there are fewer younger Chinese to replace those working late into their 50/60s and beyond (some say the Chinese pension system will collapse in about 10 years). Not to mention that the CCP's reputation is taking a battering due to their tofu-dreg construction projects failing/collapsing at the slightest thing.
Many younger Chinese people are starting to "Tang Ping" which translates to "Lie flat" because they think they have no future, and that working will not make their lives better... plus you have approx 12 million well-educated new grads each year entering the job market, which makes it overly competitive, and many are giving up as they were lied to be the CCP about their futures due to how hard it is now to find a job. China has fallen off a cliff since Xi took power... and he might not last that much longer.
Secondly, China is far too reliant on exports and much of the rest of the world is getting fed-up with the CCP's dumping practices that destroys local industries because they can't compete with the state-subsidizes Chinese firms.
Thirdly, another reason why there is population decline in China, is the same as it is for all totalitarian dictatorships and communist societies, people think it is morally wrong to bring children into such societies only to have a life of oppression, slavery, and drudgery, plus it is simply too expensive to do now with little state support... not just China, but many in the West think that far-lefty liberalism will not serve any children they have well either, and also too expensive.
People need to believe there is a good future to invest and spend, once they don't believe that anymore, then people start saving. All a self-made problem by these incompetent governments all round the world... what goes around comes around, and people will react after a while.