As the rules indicate currently, a realm is simply the sum of its cities, and this mostly works for adventurers –the more undefined or uninhabited space the better, after all ! However, if it does become necessary to know more about the realm outside of the city walls, here are some guidelines.
First, the capital’s reputation defines the reputation of the realm’s government; thereafter
The population is the capital’s population + 1d3+1
The realms ruler type will be determined by adding the capital’s ruler rating + 1d3 ;
Law Level is the capitals LL -1d6
The wealth is the 2d6-7 + the realms wealth + 1 per city
My assumption is that the national government will never be less tyrannical than the capital, but that conversely, the capital will always be the point of maximum control. Wealth is highly variable, and represents a snapshot of the economic condition at that time.
When looking at the number of hexes that a city actually controls (as opposed to influencing) remember that one subtracts 1d6 from Influence to get the rating - also, this isn't prorated if the hex is only partially habitable (or even dry land). In the map above, Kantun counts as controlling 3 hexes (0707,0706 and 0606) despite 0707 and 0606 being shared (with Ostsexan and Visaxia respectively), and 0706 being at least half water.