Josh Keating and Edmund Hugh ask some intriguing questions about national depopulation:
But Hugh’s question is an interesting one to consider. I suspect that even in the bleakest, Children of Men-style population scenarios, most countries would fight to the bitter end before surrendering their sovereignty. The exception might be places like Ukraine that have a relatively recent experience as part of a larger geopolitical entity and a large ethnic population with ties to a neighboring country.
A country couldn’t be liquidated quite as neatly as a company — even if the state goes away, there’s still a chunk of land and some people living on it to deal with. The main obstacle to countries being “dissolved” may be that other countries may not want to take on the responsibility of dealing with them — what country really wants to take on a new sparsely populated, economically stagnant region?
States can survive with remarkably low population densities, especially with modern transportation and communications technology. However, social institutions designed around the concept of stable or increasing populations got troubles. A relatively free immigration/emigration regime can resolve these issues for some countries while at the same time exacerbating them for others.
There are certainly upsides to living in a continent-spanning state. The prairie and the rust belt can depopulate themselves (although some of the aforementioned institutional problems crop up) without fundamentally unsettling the social contract.