Fixing demographic issues has never been done to my knowledge and letting demographic crisis pass will take generations.
China used to downplay that problem, until it was finally forced to scrap one child policy in favor of two child policy in 2015. That was then replaced by three child policy in 2021. Russia was debating commie era childlessness tax and offering incentives, but noting was done yet to my knowledge.
China's and Russia's rapidly growing elderly populations will become drains on resources. Both countries won't have enough young people to pay taxes needed to fund healthcare and retirement funds. Deficit of working taxpayers will lead to a lack funding in other areas and fewer workers to bolster economies. People will flee abroad due to bad economy, that will further shrink the pool of taxpayers, and cause a brain drain. That leads to a self-perpetuating downward spiral. China and Russia have to do something quick, and it will take decades to see if their fixes even worked.
Demographics alone is one existential iceberg China and Russia are heading towards but Americans do not have to deal with.
What makes you think that the U.S. won't fix its issues by implementing necessary reforms like they did in past?
America was in a similar situation back in 1860s and 1910-1930s. Despite prediction of American collapse back then, USA came back stronger than before each time. China and Russia head towards internal unrest too, and they both ended up with communism last time.
Adding some amplification, if I could.
As I understand it, Russia has a rudimentary national Social Security system, supplemented by individuals' pensions, from whatever source. China has no national Social Security system. The adult child/children are the aged parents' primary source of support, again supplemented by pensions, from whatever source.
As stated here more than once, you're running into situations where the son of a Chinese one-child family marries the daughter of a one-child family, and that son may need to be able to support as many as four parents and parents-in-law, besides himself, his wife, and any child/children they may have. Granted, some of these aged relatives may have pensions, but those pensions may not be enough. China got old before it got rich.
Japan is also in the same fix, but it got rich before getting old, and the impact of the rapidly aging population is rather more manageable. South Korea is also getting into this situation.
What is one thing Japan, South Korea, Russia, and China have in common? Very low immigration into the country.
The USA, by comparison, gets a lot of immigrants, both legal and illegal. This keeps the overall age of the American population lower than China, Japan, South Korea, or Russia. Ensures X number of workers to support each retiree.