No? A -> B doesn’t mean that B -> A. In the case of East Asia, it’s nearly a century of deliberate anti-natal government policy. China’s one-child policy is the most brutal, but pretty much all East Asian countries had softer forms of encouraging people not to have kids.
China's one-child policy is long since over, but their birthrate is very low too. Government policy isn't the problem (if it's even a "problem"). People just don't want to have big families, and now that they have a choice, they don't.
> People just don't want to have big families, and now that they have a choice, they don't.
But “choice” is individualism! There are American subcultures that are more educated and affluent than average, like Muslims and Mormons, that have much higher fertility rates than average. And that’s because those cultures exert strong social pressures to conform to expectations about family life instead of leaving it to choice.
https://worldpopulationreview.com/country-rankings/total-fer... does not show eastern countries as having particularly high birth rates, and the largest eastern countries have the lowest.
The description on that page under Africa, which is the only continent remaining with fertility rate well above replacement rate, does agree with your assessment that it's about the society and its expectations.
(As a side note, I heard that Nigeria is on track to soon becoming the country with the 2nd highest number of English speakers after the US, which stunned me given that India is the most populous country in the world and—I thought—has a fairly high percentage of English speakers.)