Segregation, the Confederacy and the pre War-between-the- States South were all controlled by the democratic party, which now garners about 90% of the black vote. Are they going to sue themselves?
By your logic, it should be the Nazis of Germany who should pay, not the entire German populations. But there are no (longer) Nazis (officially) in Germany.
So, using your Germany/Poland view and analogy, it should be the former segregationist states who should pay (and it wasn't only the Democrat-dominated South--miscegenation was illegal in California until relatively recently.