I read that book and it get so much wrong. Its views on Russia for example have been completely flattened by the Ukraine invasion and response.

Russia has successfully switched to a war economy, US companies that pulled out are co-opted by Russian ones and doing business in a more or less normal manner. Sanctions have failed, and pushed Russia closer to China (not to mention North Korea).

When you view purely through the lens of demography, you can't extrapolate to global politics.