There is no longer a government in the United States of America as would be recognised today. The hierarchy of power that existed before the war crumbled and in the aftermath a company called Horizon Technologies stepped in to take control. They brought radiation treatment with them, food and water and set up shelters and it was relatively easy to take control as what remained of the population came to depend upon the company for their basic needs. Their control grew without opposition; they built up the Complexes, provided the materials needed to maintain the clusters of buildings, the food to sustain the workforce and when the Complexes were built Horizon was already in complete control. Most don't seem to mind this, they're simply glad to have survived the war at all and to have a roof over their heads. Others are not so content, but everyone knows better than to make trouble.
Money is now nonexistent. All residents in the Complexes who reside in the apartments have a job within that Complex, whether its as a waitress or a bartender or a nurse, shelter and food are the way they are repaid by Horizon and it is not something to be sniffed at. Everyone has a task to perform and no matter how small everyone's' tasks add up to keeping the little pockets of civilisation running, no one's life is easy in this harsh new world and accepting that fact is the only way to get on nowadays.
NB. The government that led the US into World War Three obviously bears no relation to the current government. By the time the war begain there would have been a new President, obviously.
HORIZON Pre-War it was one of the world's biggest corporations, a real finger in every pie sort of company, now it is the biggest power worldwide, controlling everything within the borders of the USA from medical care to the police force, from the education system to the apartment buildings themselves. Whether residents like it or not, they are almost all of them employed by the company, it falls on their shoulders to keep the Complexes running. Horizon is mainly a faceless but ever present entity and some among the population don't think it's quite the saviour of mankind it make itself out to be...
THE MAGISTRATE Every Complex is essentially run by a representative of Horizon, this person (male or female) is usually only know as 'The Magistrate'; they report the status of their Complex to the company on a regular basis and generally keep the peace through their law enforcement officers.
THE AUTHORITY Essentially The Authority are the police; controlled wholly by the Magistrate and therefore by Horizon they handle everything to do with the law in the same way that the police today from answering domestic disturbance calls to breaking up fights outside Cavern or Rostat. In addition they protect the borders of the Complex, keeping the mutated, vicious creatures out and keeping the cowed, obedient residents in.