Don't get attached. Those cities are settlements and once you complete the requirements in reputation (win) or the queen grows too impatient (lose), you're kicked back to the overworld map to embark to a new section of the map to start another settlement. After a certain number of years, you have to go back to the main city and the entire world map gets covered in the storm, reshaping into a new map, but also clearing all settlements you built.

The reason I tell you not to be attached is cause all those settlements are temporary as they're for settlers to gather materials to send to the city, cause with the blightstorm ruining everything but the city, it's impossible lore-wise to colonize territories, so you can't really just "Settlers/Civilization" this game. and cover the map with settlements.

Won't lie, it took me a bit of willpower to accept I was abandoning those settlements, but it's needed if you are to continue as a Viceroy in this game