Fallout Inspired Nation Role Play:

There are various sizes of Nations here. . . You could have anywhere from a few hundred members up to a maximum of 1,000,000 inhabitants. Countries with more than 300,000+ citizens are likely Empires like the NCR or Caesar's Legion. If you have somewhere between 700,000-1,000,000 inhabitants in your nation, you likely have access to extremely valuable resources like clean water and electricity. 

This is 2370 AD. 270 years after the Great War which irradiated the world, the ruins of cities, the destroyed infrastructure of roads and dams, mutated creatures and animals roam what is now the wastes of America, and the rest of the world. Most of the world is without the amenities and enjoyment of the past. Fighting to survive and hoping to live through the day and wake up the next morning. Or even better, to live into middle age without getting cancer or mutating. 

Civilization is growing, and indeed, it is a miracle that it even sprouted from the ashen earth to begin with. 

Notes:
For nation creation take heed. Clean water, electrical power are two enormously valuable resources. It's even better if you can find food that hasn't been contaminated with radiation. People tend to live around their 40's and maybe live up to 50 years old, although some people can live around as long or a little longer than we do, from 70 all the way up to their 100's. Like Fallout, there are ghoul like individuals who can live for many, many years, maybe indefinitely, from the radiation. If someone is exposed to enough radiation they transform into these ghouls, also simply known as Mutants. Too much exposure to radiation at the moment of Mutation transforms them into mindless, zombie like monsters that crave flesh of anything, be they bug, animal or PERSON.

Be aware, ammunition is plentiful, simple weapons of the past, like certain rifles and pistols are also abundant, but very powerful weapons capable of harming tanks, etcetera will be more rare. There are even weapons like lasers and plasma weapons. Exceptional circumstances can allow people to fly through the air in rarely seen aircraft. Among the most rare of all military assets a faction these days can have is an air force. Be ecstatic if you can find more than a handful of jets/planes in the air in working condition.