Why was reconstruction so problematic?

Life differed vastly between the Northern and Southern states. Social, political, and economic ideals in these regions were strongly held, and the bloody Civil War only worsened the tension and strife between Northerners and Southerners.
Additionally, slavery was the backbone of the economy in the antebellum South. The abolition of slavery and the South's defeat in the war resulted in severe economic strife. Many wealthy families in the South saw their highly productive and lucrative plantations fall to ruin.
After the war, Americans in the South were none too eager to rejoin the Union, making diplomatic efforts all the more difficult. There was severe resistance to the reunification of the states, and many in the South were unwilling to accept defeat. They viewed a centralized federal government as oppressive, valuing more influential state governments.