Republic of America
The government of the United States had collapsed due to non-participation in the years of the plague, and the surviving city-states fended for themselves for only a little while; then a new government declared itself to be in effect, and the Republic of America was born.
The government is a true Republic, with an elected Senate consisting of representatives from each major population center. The initial elections in some areas only offered one candidate, and in other areas, the defeated candidate then was hired to serve on the staff of the winner; as a result, there were some public misgivings about the actual element of representation. Political protests are tolerated, and many of the leading protesters have, since the founding of the Republic, become successful politicians and even Senators.
Denver is the capital, strategically chosen as the largest and best-developed metropolitan area – and one easily defended from large-scale assault. Denver also houses the headquarters of the Smith-Phillips corporation, along with dozens of contributing and competing companies, as well as the Denver Institute of Technology and Design. All the same, the various city-states of the Republic tend to identify locally rather than nationally – which suits the national government fine, so long as everyone still pays their annual taxes.
The old military stockpiles of the United States have been seized (with justification, of course) by the new Republic. While much of the equipment is shockingly out-of-date, it’s still deadly and commands respect. Gas-powered tanks have, in many places, been airlifted and cemented into rows to form weaponized blockades around sensitive locations. The Republic has declined to dismantle the remaining nuclear weapons, making it one of only two governments known to still have them.
Of course, it has some ongoing issues with the American Confederacy of Independent City-States, with which the Republic overlaps significantly.