It seems to me that the importance of the Civil War was not that it made America somehow different, which it undoubtedly did, but that it fulfilled Abraham Lincoln's aim of preserving the Union. If there had been no war, or if the South had won, there would have been two nations in the middle of North America. One of them would be spreading slavery clear across the continent and adding a larger and larger slave population to states and territories. Would slavery have been ended even now in the 21st century? Or would there be ten times as many slaves with ten times the injustice and cruelty? What would have been the relations between these two nations with different economies and different values? Wouldn't a bigger and much more costly civil war become inevitable? Or is it conceivable that the institution of slavery would somehow dissolve in the Confederacy over a period of several centuries? I think we have to take Lincoln's word for it that the war was worth it because it was vital to preserve the Union in order to preserve democracy.
Without the Civil War, Racism and Slavery against Blacks would of continued, and would of been worse in the 1900s than we experienced.