That's not enitirely true. The American Dream was (and is) settler-colonialism. Early settlers were promised free land if they killed indigenous peoples living there already, which led to a mostly self-sufficient labor class that could use its self-farmed land as a means to support themselves while bargaining for higher wages. If you were a white man, this dream was attainable, period, even if it meant enslaving and genociding millions of people.

Then came the post-war period. The wartime economy was still fairly planned, and aimed at full employment. Further, the US was emerging as world hegemon and de-facto empire. Imperialism and social safety nets largely expanded due to needing to provide better metrics than the Soviet Union was providing again kept the white men of the US living in the American Dream.

Now that imperialism is decaying, and social safety nets have been gutted along with the fall of the USSR as the main rival power, even white men are starting to fall into genuine proletarianization at large. The US is still a settler-colony, but its one where finance capital has dictatorial control yet imperialism is waning, and where many industries have been hollowed out and shipped overseas because imperialism was more profitable. The US is working its way to its own demise.

Yes, I absolutely agree that the disparity we see today is a direct result of the former social relations. The agrarian slave-driven economy in the south was certainly going to result in conflict with the industrial economy based on wage labor in the north, especially as the north needed new wage laborers to expand industrially. Historical progression is a process of endless spirals, tendencies and trajectories accumulate over time until a quantitative buildup results in a qualitative change.

However, I don't see it as something that was intentionally planned. Capital doesn't think that way. Capitalist production is an ever-expanding circuit that must constantly be repeated, anything going against that system of voracious profit gets dashed. Long-term planning is characteristic of socialism, not capitalism, nor the semi-yeoman style of settler-colonial capitalism or slave driven agrarian economy.

This is important, because understanding how we got here today can tell us where we are headed. The historic task of the US proletariat in the age of dying imperialism is to topple the capitalist state and replace it with a socialist state, focusing on decolonization and anti-imperialism. The old world is dying, and the new world struggles to be born. This is only increasingly possible because the US working class is becoming increasingly proletarianized due to monopolist capture of the land, and imperialism is weakening to the point where we cannot be bribed as much by its spoils.

We aren't here because of some 5-D chess from the old bourgeoisie, nor did the settlers have ignorance of the system. The US settler class was bribed using the spoils of genocide, and its only increasingly true now that there isn't really a semi-yeoman class. The immense brutality of settler-colonialism can't keep the US afloat anymore, nor can imperialism.

I'm just trying to help provide a Marxist perspective, as it genuinely gives us a chance of completing the US proletariat's historic duty. I'm a Marxist-Leninist.