Now that you mention it, it does give off those 5th Element vibes. Though, The Endless Nation is actually comprised of Native Americans, so it’s the complete opposite of aliens in both the extraterrestrial sense and the immigrant sense.
No one really knows what went down, but at some point they went into isolation for a considerable time, then emerged as a technological superpower. As the comic puts it:
There is no record of the internal revolution which resulted in the Machine State, only the oral history of cast-out believers who now reside in the dead country. One day there was no Machine State, and then the next there was.