I've just used a classic name for the genre. I'm a big fan of Cities: Skylines.

At a country scale some simulation techniques need to change. For example, tilemaps become ridiculously inefficient (a byte per 10m^2 becomes tens of GBs), so they either need some form of compression, or the simulation has to use vector-based maps instead (more like Cities Skylines).

Another quirk is that at a country scale agent-based simulation becomes less interesting, because individual agents don't influence much, only their collective behavior is big enough to matter, and that starts looking just like a normal distribution of the simulation data you put in.