CMV: In the long term, China is the declining power, not the US
When Xi Jinping invoked the "Thucydides Trap" with Trump in Beijing last week (link), he was framing China (PRC) as the rising power and the US as the established one struggling to make room. The demographics tell the opposite story. China is the country in long-term structural decline relative to the US, and Xi's confident framing is partly projection.
I want to lay this out and have it challenged. My claim is that the combination of (a) China's demographic trajectory and (b) the US's relatively unique capacity to integrate immigrants at scale means that by mid-century the gap will be widening in America's favor, not China's.
The demographics
The key metric is the potential support ratio (PSR): working-age adults per person aged 65+.
- 2026: China 4.6, US 3.5
- 2050: China 1.9, US 2.7
- 2100: China 1.5, US 2.6
China starts ahead, falls below the US by mid-century, and the gap widens from there.
Xi knows this. His administration has thrown financial incentives, social campaigns, and policy reversals at the fertility problem for over a decade and none of it has moved the needle. The pattern is regional and policy-resistant. From South Korea's cash incentives to China's pivot from one-child enforcement to three-child encouragement, decades of pronatalist effort across East Asia have produced no sustained reversal.
The assimilation advantage
The US has roughly 46 million foreign-born residents. That's more than the foreign-born populations of Canada, Australia, the UK, France, and Germany combined. The second generation economically converges on the native-born baseline and self-identifies as American at very high rates. Canada (~23% foreign-born) and Australia (~30%) post stronger per-capita assimilation numbers, partly because they pre-select harder for skilled migrants through points systems. But neither runs this model at anything close to US scale. Canada's entire foreign-born population is smaller than the foreign-born population of California. No major country can do what the US does. China cannot; Japan and South Korea have not; Western Europe has tried and struggled.
This is the lever that lets the US partially offset the same demographic drag hammering every other developed economy.
The Trump Factor
The current Trump administration is actively damaging the advantage I'm describing through two channels:
First, an alliance with oligarchs (tax cuts skewed up, gutted antitrust, regulatory capture) widens the gap between rich and poor and corrodes the credibility of the American promise that anyone can do better than their parents.
Second, explicit racialized messaging tells the second generation their citizenship is conditional on ethnicity rather than commitment, which is the most direct attack on the assimilation engine I can imagine. This shows up concretely in erratic visa, green card, asylum, and naturalization policy that signals which immigrants are "wanted" and pushes ambitious people to plan their lives elsewhere instead.
I will concede this: Trump was right that the Biden-era border situation had become unsustainable, and enforced limits at the border are necessary or the political coalition for legal immigration collapses. The problem is that the response has bled into the legal channels that are the actual source of US strength.