"America is a political cesspool because the Confederacy wasn't punished properly."
This point simply doesn't make any sense. What is proper punishment? What punishment did the Union fail to enact that would have saved modern America?
Yes, the South's, who had the greatest incentive to continue slavery. But, the economy was truly transcontinental. One economy. The North benefitted immensely from slavery.
Do you think the North would opt for a punishment that would amount to falling on their own sword? Could such a punishment be politically tenable?
what.
Human beings "other". It's key to understanding our species. So long as hardship can befall a people, those people will find a scapegoat. To this day, Blacks are only 14% of the population.
Capitilism + Humans = Political Cesspool
Punishing the Confederacy, even by wiping them off the face of the planet, would not have changed what America was to become, except by delaying global American hegemony.