I don't think slavery really explains much. The Southern States' economy was dwarfed by the North. Did slavery benefit the US economy? Of course.
I would argue the US' protection from the ravages of WW1 and WW2 led to its economic power. Before WW1 the US wasn't a major player on the international stage.
I would argue the US' protection from the ravages of WW1 and WW2 led to its economic power. Before WW1 the US wasn't a major player on the international stage.