In 2025 during a time of strife, religious upheaval, economic downturn and general unrest the elected President refused to step down, and backed by the military, made himself dictator for life. He ruled with an iron fist and forced unjust laws upon the people. He played a major role in the destruction of Europe during two of the worst world wars history had ever seen. Before he died he forced the government to recognize his son as the next dictator to carry on his legacy. His son did just that. He invaded Canada, and after killing and driving out the majority of the population, turned the country into the United States' own personal oil field. He implemented a state of isolation and cut off all contact with other countries, controlling both travel and communication. And then in family tradition, named his own son as dictator on his deathbed.
In 2250, there was a great storm that destroyed half of the country. The Midwest, from Ohio to Utah, became barren wasteland. Completely uninhabitable. New Mexico, Texas, Louisiana, and the entire country of Mexico fell to the bottom of the ocean, like a modern day Atlantis, killing millions. Like Pompeii thousands of years before, the Hawaiian volcanoes suddenly erupted, covering the island in destructive hot lava. Much of the technology and knowledge that the dictator kept hidden from the people was forever destroyed- thousands of years of learning and advancement lost in a matter of days.
The dictator did nothing to ease the suffering caused by the storms and the people eventually rebelled. Factions were formed based on geography. Working together and storming the capital they seized and imprisoned the new dictator and his family. But rather than remove him and return the United States to a Democratic Republic, these factions then fought with each other over who one should hold supremacy.
Soon the country was ablaze in the most destructive civil war in history. There were no winners, only survivors. And the survivors picked up the pieces and formed a new way of life- each area, or faction, became its own small kingdom. Some thrived, and some did not.
Eventually what was once the United States of America, became six well established major kingdoms.