This concept, The City-States of America, is similar to that of the primate city, a term coined by Mark Jefferson in 1939. A primate city refers to a city that is disproportionately larger than the other cities in that country or region. This idea is related to the Zipf distribution, a scale-free or power law distribution that often describes the ranks of the city sizes within a single country. In these distributions there many small cities dominated by a small number of extremely large cities, whose sizes are described by the exponent of the fit of the power law.
An explanation for how such an even distribution can occur is that of Gibrat’s Law, which posits the idea of proportionate growth — larger cities grow proportionally faster — can lead to this long tail of city sizes. A recent scientific paper that explores cities and Gibrat’s law is found here.
it is fascinating to note that the concept of proportional growth is a pattern. You can see it with companies, products and even ideas.