What was significant about the strong spirit of nationalism that appeared in America in 1815 to 1824?

Americans were building the industrial infrastructure, the competitive marketplace, the urban spaces, and the transportation system that they would expand further and come to rely upon in the latter half of the century. They were grappling with many changes: the rapid growth of cities; the emergence of hourly wage work conducted in large factories regulated by clocks. Above all, they continued to wrestle with the contradiction at the heart of the era: the existence of chattel slavery in a country dedicated to the proposition that all men are created equal.