The chief way the antebellum or pre-Civil War South differed from the North was that in the South slavery was legal. This had a profound impact on the ideology of the two regions, especially in the South. While the entire country was racist and many Northerners either supported slavery or assumed it would gradually wither away, whites in the South, as time passed, more and more aggressively defended an ideology that claimed slavery was beneficial to both blacks and whites. Slavery was considered by some a system of benign paternalism that offered blacks cradle to grave security. Christianity in the South was used to normalize slavery as a biblically sanctioned institution, and slaves were admonished using the Bible to obey their masters. The economy of the South, almost entirely agrarian, depended on the very cheap labor slaves provided growing and harvesting sugar, tobacco, and cotton crops. Therefore, whites worked very hard to justify slavery not only as a necessary evil, but as positively good system of social organization that helped "civilize" inferior blacks.
In the North, even before the Civil War, the economy, though heavily agrarian, was also much more industrialized, with many mill towns and factories, and, of course, no dependence on slavery. Therefore, an abolition movement was able to grow in that region, and Christianity was used ideologically to support abolishing slavery.
The slavery issue put a deep fissure in the sense of the nation sharing core ideological values. The South defended slavery, while many in the North perceived slavery as contrary to the country's fundamental values of liberty and equality. Eventually, this fissure could only be resolved through a civil war.