I have a world where its mostly in ruins. But its run practically by corporations and smaller factions. A large part of the world is recovering from ecological collapse, massive pollution that travels by air and sea, warfare, lingering effects of bio and chemical warfare etc and intense radiation in certain areas. Essentially the environment is decaying. Basically, the world of Armored Core 4/4A if anyone's familiar with it.
The story takes place later, where there is some reclamation of land pollution cleaning attempts. While large swaths of land are uninhabitable or non-arable, there's just enough safe zones to form larger factions that somewhat resemble early nation states.
One of the issues I had was with food production. I want to make crop yields limited, essentially a food scarcity of sorts or the threat of a bad harvesting season causes major problems across the world. My research and some conversations have led me to the fact that a modern society with decent technology can make some pretty resilient crops. That and seeds/plants by themselves are pretty resilient. Chernobyl for example has fauna and even edible plants growing around the exclusion zone. Israel has done significant work in growing crops and making some very tough plants and seeds as well.
Why would an otherwise near future/modern world with advanced technology in a somewhat post-apocalyptic/ environmentally challenged world struggle to grow crops/produce seeds on a consistent basis for the foreseeable future? Even if said world is on the slowest of slow paths to recovery when it comes to arable land
Population for factions can range from city states to small countries or confederations.