Your view of American History seems narrow. If I take a narrow view of the history of my Family in America the narrative is much different. We did not have any of the phases you described, no slavery, no segregation and no stagnation. Three centuries of constantly improving standards of living, yes my family’s history goes back to before the American Revolution. While slavery was legal in New England it was rare in the northern part of the region. My family prospered without slaves and prospered mostly on sustainable extractive industries for the first century or more. Logging, Farming, Hunting, Fishing. There eventually came industry, woolen and paper mills but still not slaves or segregation unless you mean that the poor whites lived in the poor section of town or in a trailer in the woods. Our standard of living improved with better shelter, electricity, running water, schools, paved roads, churches, parks, etc. No one was subjugated and no groups was exploited. The mills were for the most part not unionized but still received fair pay and benefits. It was not until the 21st century that racial segregation became an issue in Central Maine and that was not even from the dependents of slaves but was from refugee resettlement and these refugee’s self-segregated, it was a failure to integrate.
You need to get a handle on “there is no one American Society” we are Yankee, Rebel, Urban, Rural, Left Coast, Gulf Coast, Snow Bird, Texan, Rust Belt, Heart Land, Appalachia . Very much of this country did not go thru the evolutions you talk about. How long have you lived in this country and how many different places have you lived (not just visited but put down some roots). I have lived in New England, Florida, California and Louisiana with a decade of living in each place. I have seen this country from a variety of vantage points. I think what you believe you know of this country is based on what you read in the news and from you close associates. About the only groups of people in this country I have not worked with are the Rich. I have worked with all the types of working people.