Turtledove nailed it in his novel series: the Union and the Confederacy would have been locked in episodic war forever, like France and Germany and France and Britain --- plus maybe one or more new countries from the territories.What would have happened if the Union allowed the confederacy to secede in 1860?
150 years later, the old confederate states are dominated by racism and are not in sync with the majority of the Union.
In 1860 they were Democrats, in 2022 they are Republicans but the morals and government desires of the South have not changed.
Should we jettison the old confederacy, plus a few other states, from the Union in 2024?
I will never know why Britain and France didn't support the Confederacy so that the United States would be broken up and Britain maintained in its superpower state.