That’s fascinating, since it means that both the USA and Russia will remain largely depopulated hinterlands (comparatively) throughout the next century or two, though I expect the USA will end up birthing several different nations from the populations presently within it’s borders as the demographics shuffle and re-entrench themselves into sustainable growth patterns.

The emptying world will experience major economic and political changes as people simply disappear. A world empire like the US’s may become impossible. The European colonial expansion occurred with a young, rapidly growing population, not an elderly, shrinking population.

So, there won’t be any Chinese to colonize Siberia, nor any Russians to resist them. Siberia will once again become the property of the local tribes. Will we see neo-Mongol steppe warriors once again?

And Canada, might that revert to the Cree and Inuit?

They’re both large, continent spanning, resource rich, highly populated (but lacking in density), diverse, geographically isolated countries with rather extreme ideological tendencies with strong but increasingly distant European roots. Each of them has the potential to experience massive internal strife because of these factors, but the precise manifestation is a bit different in each case.

In the case of the USA, the diversity is largely blended together, geographically speaking, resulting in a population that responds very quickly and violently to the presence of differences, forcing minorities to feel the need to band together in disproportionately intense ways while their assimilation is taking place. This benefits the central government because they bind the minorities to themselves over time by acting as protectors of their rights against local majorities, while also diluting any explicitly self-reliant ethnic politics (it does encourage unspoken ethnic corruption for a time however).

For Russia the diversity is highly segregated and rooted in separate histories, meaning the various populations seldom have to interact with one another, lowering overall tensions between populations. Conversely, there can be no meaningful assimilation because the cultural nucleus of each nation is intact. It’s not the minorities that have to deal with the Central government as protector, but rather their local government becomes their protector against the Central gov’t, and the Russian central government doesn’t have to court the population by protecting their rights, but rather the local government by offering them power/wealth in exchange for cooperation.

It actually goes a long way in explaining why Native Born Americans prefer local government, and view the Central government with hostility; they’re situationally akin to the minority Republics within the Russian Federation, without the advantage of explicit ethnic identity.