War. War never changes...
When nuclear fire rained from the sky, a lucky few took shelter in great underground vaults. When they emerged, they banded together to face the harsh conditions of their new home... the wasteland. Some formed democratic societies, like the New California Republic...
Its been over twenty years since the fall of Caesar and the splintering of his legion, the wasteland regions are rather peaceful. People are spreading the borders of what they are calling 'civilized territory', places with what they call proper governments and little remaining tribal identity. Independent New Vegas limits the spread of the NCR to the west but allow Californian immigrants who wish to leave the oligarchic republic. This leaves only north and south to expand, so settlers have been moving into the new states of Baja and Oregon. New Vegas, ever the city state, has mostly been expanding the city itself from the ruins of the Legion war. The hoover dam is at full operation again, providing electricity for Vegas, and a good portion of California (for a good fee of course).
Since the fall of the Dam and deaths of both Lanius and Caesar, the legion has practically fallen apart. Caesar himself survived the battle, but not the year. His cancer caught up with him in the end, and he expired. With it, went the legion. While loyalists promoted one of his surviving his commander to someone they term "Augustus", a successor who claims to be given power by the god Mars, he has only a fraction of a power and support. Most of the Legion has broken apart into small, almost tribal groups, or settling into semi-nomadic raiders. As a result the former territory of the legion has been broken up into what's known as the 14 Remnants. The borders shift nearly constantly, but every power base has largely been held since the establishment of each Legion.
To the south the Mexican tribes, called Cartels or Calpolli fight for dominance, with a few city states forming from the normal chaos. Along with the fall of civilization, the native populations found a resurgence. The Cartels are made largely of the Spanish Mexican population, and Capolli of the native Mexica and Mayan peoples. The largest city states known to the NCR are Lapaz, Obrego, and Ciudad on the borders of Caesar's legion. The people in the south are fiercely against settlement of the Californian Republic, displacement already pushing more of the tribes down towards the unknown center of Mexico and the mythic city states of Tenochtitlan and Tikal.
The north is full of Cascadian tribes and cities, with the largest single entity being the Metroplex of Seattle, which stretches down the Interstates to encompass most of Portland as well. The push northward has earned enemies everywhere, leading to slow expansion as well. The Metroplex is the most welcoming of the polities here, though its only because they've traded with the Hub extensively for years. With the destruction of New Canaan years ago, most of Utah is sparsely populated, and the Mormon tribes struggle to survive against the still legion aligned tribes in the area. Its a rather dangerous area to the north, the colder winters and high mountains making much of it unable to be inhabited by the more southern Californians.
Hemmed in on all sides, the NCR has begun looking into other ways to expand its power and trade, without the costly wars of decades past that they have yet to recover from.
Spearheaded by a few companies from the Hub, under ghoul Ferrous' and his company's supervision, an expedition across Wasteland America to explore the various regions has been created. For better or worse, several mercenaries and other wasteland wanderers have been hired to help provide protection and various services for this expedition across America. They'll face a myriad of dangers, especially far away from settled civilizations and towards the more tribal lands of the center of the USA. The protective tribes, post-war cults, monsters, and the simple lack of resources will make this trip dangerous. Its more than likely not every member of the expedition will make it from one end to the other, and indeed some are given the option to leave with a fraction of the money they're offered for going the full trip.
Whether their motivation for this trip is purely monetary, curiosity, or idealism, those involved will risk life and limb to help this journey succeed. This trip will likely likely will take months if not years to complete. Those who go on it might not ever return to their old homes. The old maps of the United states may have the lay of the land, but they list none of the danger you can find along the way. This trip is one of discovery, to see if any other nations have risen out of the ashes of the United States, or if the NCR has the only and best chance to recreate the world in its image, and that of the long dead America.