I agree as far as it goes. I do have to note that one important omission from the story of the US is empire. In addition to the “internal” forms of oppression you describe (slavery and segregation) that motivated growth for two centuries, there was also the external. The acquisition of vast amounts of land and resources through genocide of indigenous peoples, the expansion beyond those boundaries by conquest, the prying away of colonial territories from the dying European empires, and the establishment of a new American Empire founded on military might (including the nuclear arsenal) and economic exploitation.
While I think it’s an excellent point that the period of stagnation that began in the 1970’s immediately followed on the end of segregation, this period also followed on the US defeat in Vietnam and a decade that had seen numerous developing nations declaring independence and either aligning themselves with US rivals (the Soviet Union and China) or becoming n0n-aligned.
Finally, I think we need to take the external conditions of US growth into account because the period of stagnation emerged and persists *even though* the US is still a global empire with coerced access to huge international markets and natural and human resources. Or to put it another way, the economic system in which we live cannot provide a decent standard of living for much of the population despite having the fruit of oppression in the form of billions of dollars of corporate profits pumped into it each year.