I don't know if it's God's will or not, but it has been very fortuitous that a unified, Christian land controlled the continent of North America, secure from any European power and able to defeat any empire that sought to control the world.
Correct. We would have been no different than the Balkans if not for Lincoln. An independent South, with it's slave population doubling every 20 years and offering little attraction for white immigrants or even in retaining the yeomen class would have been forced to expand to diffuse there slave "property" over a wider market area or face the certain collapse of the "peculiar institution" and the likelihood of death at the hands of their slaves who would have vastly outnumbered them.
The very root of the conflict stretching back to the founding was over expansion of slavery to the west. Southern independence would not have changed the fundamental economic fact that slavery had to either continually expand or face complete ruin. It was the ugliest of Ponzi schemes.