The North
LOST the Civil War. The south rules the USA, especially the lying crooked trio of Florida, Louisiana, and Texas, robbing our country blind and turning it into a second rate country of freedom-loving yahoos.
The freedom being the freedom to be greedy, treat people like rubes and commodities, and to pollute at will while making a killing. The freedom to have an avaricious military-industrial complex wasting our taxes and waging wars around the world, toppling other countries and being based in hundreds of places around the globe while our nation goes unprotected and uninsured.
If the slave holding South didn't want to stay in the USA, we should have let them leave and expand into the Caribbean and Central and South America. Why would we want to be associated with people who can own slaves? The North should have kept expanding to California and fought to keep that. Slavery would have died of its own anyway. Economically, oppressors do better with wage slavery and sharecropping than having to feed, clothe, care for and shelter slaves. Reconstruction and Jim Crow laws lasting a hundred years more made the legacy of slavery last to the present.
If we had left the South go, instead, imagine a Western Hemisphere today more along the lines of having two or three more Canada-like nations but with better weather stretching to the northern parts of South America, with more English being spoken.