That’s only true if we cutoff immigration, which is how the US has offset the downsides of lower fertility.
Even if we can’t defer those problems forever, we can slow down the transition, making it less painful than the one experienced by Japan.
Even if we can’t defer those problems forever, we can slow down the transition, making it less painful than the one experienced by Japan.
Japan is trying to increase its immigration for the same reasons I mentioned, and they're struggling for the reasons you mentioned. Only 2% of their population is foreign born[1], which is up from past figures, but still a drop in the bucket compared to the US system.
You're totally right that there's going to be political and cultural issues over immigration, there always is. But America has the political and social institutions necessary to maintain a high level of immigration over long periods of time, which can help damped the blow of fertility change even if it's insufficient to fully reverse the trend.
0 - https://www.pewresearch.org/fact-tank/2020/08/20/key-finding...
1 - https://www.oecd-ilibrary.org/sites/e025d47d-en/index.html?i...
You're safe for at least 50 years.
Even when global populations begin to fall, we can still keep immigration up. There's nothing at all inconsistent with falling populations and immigration. Economically there might be a lot of pressure for people in places with falling populations to emigrate, because of the economic effects of sudden population drops.