If America couldn’t have expanded westward, would the Civil War happened? Would it have happened without that opportunity for a massive trade imbalanced based upon the divergent costs of labor under respectively slave-holding and purely freemen societies?
Prima facie, this seems to be useless musing but it truly isn’t. It may be a very important question.
Face facts, the Civil War wasn’t a war to free the Black slaves per se. Nobody of any consequence wanted those slaves freed and even the rank and file Abolitionists favored a fanciful deportation / repatriation strategy.
Both the Civil War and most of the serious problems that led up to it were over allowing slavery to expand westward, either by the Southern states or, after the Secession, by a foreign nation. Business interests in the non-Slave states knew that they couldn’t compete against slave labor.
That was then and this is now, and that now includes America not being able to effectively against China, to lesser extent the rest of Asia, and the Developing World where, once again, what amounts to slave labor is used.
That is certainly worthy of consideration.