First of all, the North was notably Puritan Republican while the South was heavily settled by Scots, Jacobites and Cavaliers which is why some historians believe the American civil war was a continuation of the English civil wars. In some Confederate war poetry, Yankees are referred to as Puritans and Southerners as Cavaliers.
Second, the initial animosity between North and South was economic.
Southerners produced raw materials which were sent to Northern factories to manufacture into finished goods. The US government placed high tariff taxes on foreign made goods. However, foreign raw materials were free of tariffs. Thus Northern industry enjoyed tariff protection for Northern finished goods... while Southerners struggled with foreign raw material competition. The South either imported finished goods or had them shipped from the North. Because import tariff taxes were cheaper than shipping costs from the North, Southerners actually paid most of the tariff tax money coming into the federal government coffers [90% of US government revenue at the time.] The federal government used that Southern paid tariff tax money to benefit the North by building more Northern infrastructure [roads, railroads, canals, etc.] Southerners rightly believed they were being intentionally economically exploited by the North. The irony is... economic exploitation by the North on the South extended to Southern slaves.
Third, the civil war was a fight over individual states rights versus a strong centralized US government. Many Southerners share my belief that the American republic died in the civil war and the American empire was born. This is primarily because the individual states lost much of their power and are now ruled over and dictated too by a strong central government.
