There has always been racism, and slavery.
Its the deliberate conflation of the two that I find particularly vile, and that has been especially exaggerated in the USA, especially when it was applied to plantation agriculture in the southern colonies.
Similar economic motivating factors occurred in South America under Spanish and Portuguese rule, but nowhere has racial conflict persisted as long or as violently as it has in North America, particularly (but not exclusively) in the old Confederacy. The exception is, of course, Canada; but the Canadians have always had the Quebecois to pick on. Perhaps its just that the Northern European, Anglo-Saxon, Germanic and Nordic races are just naturally more racist than other European stock. Its in the blood. 8)