I found this modded server called Iperios and it is all about making nations. You can start your own nation and choose how it is run. You make your own government and your own laws and your own ranks. If that sounds like too much work you can just join someone else and help their nation grow.
The server runs the Allthemods10 modpack on version 5.3.1 so you need that to play. You have to join the server discord first and ask to get whitelisted. Then you read the new player info to get the IP and some basic tips.
When you first join a staff member helps you. They guide you so you know what to do and they give you a beginner kit. After that you are free to start building and join or create a nation.
The rules are not fully listed but it feels organized and pretty friendly because you talk to staff first and you have to get whitelisted. It seems like a good place if you like modded Minecraft with more politics and nations instead of just solo survival.
