Of course, this is a rhetorical question.
Lincoln was America’s most consequential president; world history would be very different if the United States had broken in two in the mid-19th century.
The result would have been an industrialized North with a strong central government, and an agricultural South with a weak central government. Whether slavery would have continued isn’t really an issue, because eventually mechanized agricultural would have displaced slaves, and “the peculiar institution” would have withered away. Even before the Civil War, many southern thinkers realized slavery was on the way out.
Lincoln didn’t fight the Civil War to abolish slavery, although it certainly was the central issue of the war, and the one that sparked the war. He fought it to keep the Union intact, and was willing to make concessions to slavery to achieve that goal. The Emancipation Proclamation only came after the war had been underway for some time, and was drafted as a temporary wartime measure designed to put pressure on the South.
So the real question is, was keeping the union intact worth the loss of lives? Slavery’s evils make it relatively easy, or at least easier, to answer “yes.” There’s a question whether the war otherwise could have been avoided, because the sectional conflicts went deeper than just the slavery issue. They were two fundamentally different cultures and ways of life. And, as I’ve pointed out above, the war wasn’t needed to get rid of slavery, because it would have gone away in time as a result of the natural evolution of technology and the economy.
One thing worth mentioning, though, is that if the Confederacy had become a separate country, the legal slave trade — banned by Congress in 1807 — likely would have resumed. How much difference this would have made is hard to say, however, because illegal importation of captives from Africa continued right up until 1859. But it seems likely the ban on legal importation reduced that trade.
Because the United States did not split up, it became a superpower. That probably wouldn’t have happened, at least not as much, if its northern and southern sections had remained separate countries to the present day. However, it’s conceivable the South would have rejoined the Union after slavery died out, as there would have been mutual advantages in reunification. In which case, the trajectory of world history, and the USA’s impact on it, might have been the same or very similar.
But one can play with the “ifs.” For example, what if the CSA allied with Germany in the world wars? What if running border conflicts between USA and CSA had diverted Americans’ attention and resources away from world affairs, making us an isolationist people with much less influence abroad? How would a divided America compromised North America’s support for the European democracies and its ability to resist Japanese and Communist aggression in the 20th century? Would USA and CSA have worked together in the Cold War? If so, how much, and how well? There is much to ponder here.
The fact is, the United States did become the dominant world power, play a decisive role in the world wars, win the Cold War and facilitate the disappearance of Soviet communism, and become the world’s strongest, most prosperous, and innovative economy. And we did all that together.
There’s no real need to ask how all that might have been changed if Lincoln had let the South go, because he didn’t, and that’s how things worked out. Looking back on what did happen after the Civil War, it’s clear we’re all — including southerners — better off because things turned out the way they did. We have our disagreements, but that’s always been true. Today’s politics are contentious, but not as contentious as the politics of the Republic’s early years or the years leading up to the Civil War. We’ve been through much together, we and our ancestors, and what emerged from all that turmoil is the most successful society in human history.
Given that outcome, it’s very difficult to argue that Lincoln was wrong to hold the United States together by force, despite the terrible cost of doing so.
From the beginning of the United States until the civil war there were multiple times a state or state threatened to succeed. Andrew Jackson threatened to remove the head of a states governor is the state succeeded. The events taking place in Oregon illustrates the one basic problem with any state succeeding and that is federal property. It existed in every southern state. Ft Sumter where the first shots are fired was US federal property. If President Buchannan been more active the Civil War could have been averted. Or at least the number of states that succeeded reduced.
Lincoln was fully aware his election could have meant succession and civil war and he made clear in the time between election and taking office that the south would not leave the Union without there being war and Lincoln intended to fight to keep the Union together. The US Constitution and the oath of office gave Lincoln no choice as it gives any President no choice on the matter. Lincoln knew that before even running for office. President Buchannan more than any other individual made succession possible and war inevitable.
Even assuming southern states managed a peaceful succession what about Kentucky, Maryland, West Virginia, Delaware, and Missouri? And do the southern states get southern territories and some sort of split of California so the south can have a port on the Pacific? Then the south invades Cuba, Mexico and fights a war with Spain, while the north goes to war over Canada, with Great Britain. No reason that slavery would not exist to this day in the south. Perhaps no WWI as the European powers kept the peace in order to fight in the Americas and keep the Americans down with everyone getting a bit of America.
We cannot understand today how much the election of 1860 really was an election of change. Not only was Lincoln elected but so were the Republicans who had the votes in both houses of Congress to make mahor changes. At minimum to pass legislation undoing Dredd Scott. End the fugitive slave arrests in the north. Ensure slavery did not expand.
Rather than engage and simply accept the consequences of the election of Lincoln southern states began to succeed. Even New York city threatened to succeed. Lincoln prior to his inauguration clearly stated his opposition to succession and wanted a peaceful solution but only Union being the only acceptable outcome.
Lincoln forced those who wanted succssion to turn to violence by attempting to resupply Ft Sumter. This was one of the politicly brilliant moves by the President. There was no invasion by an aggressive North prior to Ft Sumter. While Virginia and Tennessee succeeded Kentucky did not. West Virginia becomes a new state. Lincoln did have a choice in preserving the Union by force, and he would have accepted slavery within the Union to preserve it during this period. So it is the counter movement to the election of 1860 that is wholly responsible for the Civil War.