Final answer:
The United States lacks a primate city due to its historical development, where multiple cities grew in importance across the large and resource-diverse country, and advancements such as an extensive highway system, which distributed the population more evenly.
Step-by-step explanation:
The United States does not have a primate city due to its unique historical development and a more distributed pattern of urbanization. Unlike many European countries, which often developed around central cities that contributed to their identity and economy, the U.S. saw the rise of multiple important cities that contributed to its growth. Several factors played a role in this, including the availability of natural resources across the expansive country, which resulted in different areas specializing in different industries, and the historically significant federal system of government that encouraged the importance of both national and state capitals.
Additionally, advancements such as the Federal Highway Act in 1921 allowed for improved transportation infrastructure, which led to an increase in mobility and a more balanced population distribution. Without a single city holding a dominating influence over every aspect of American life, cities like New York, Los Angeles, and Chicago have all become highly influential, yet none overshadows the others to the extent required to be considered a primate city.