Ok, for you this is more about taking sides than assessing real history then. Thanks for outing with that.
But anyway I'll play. At its formation the United States was unified on allowing slavery, so to directly contradict you, yes there would be a United States. Slavery was not yet a war causer.
You at least get a point for originality.
That's not so. High school World History textbook on this one.
I nearly agree there, in that there was a gross error in the Constitution. The question of slavery was left to twist in the wind, and it did. Amendments addressed that.
I have no idea how I am taking sides here. I do not know what the sides are.
Tom Jefferson attempted to place anti-slavery phrasing in The Declaration of Independence, but that was a no go. Had slavery not started in North America, we would not be having a discussion about it. But, it did start.
Nobody seriously tried to end slavery by the Constitution. The Age of Enlightenment did not shine very brightly at times. If one batch of well to do White Elite started to object to slavery, another would point out that the US could not get on very well with rum running and salting cod. Tobacco, rice, indigo and cotton could provide for world trade, was providing, and nobody could figure how to do it without slavery. They also could not figure any way to fund a government except by imposing on imports. Not very imaginative people, I'd say. What side does that put me on?
President vs British monarch?
Edited.
Lack of imagination. When those fellows were having their game of writing a Constitution (nobody asked them to do it), they amused themselves by mostly copying State Governments, which had generally mimicked the British System. They maybe got tired at points...really tired when creating the executive .."let's just throw it all into one, a president, like the states have...he can't do much without the Speaker of the House, anyway..let's get something to drink." Oh, they dealt with slavery, they kicked a 3/5 can down the road, along with a method of revenue and a real system of defense. Can kicking, real imaginative. The ones that could look beyond what was happening could rationalize "i won't be around to see it,".
The political split happens. No war.
But Lincoln cannot allow the country to split because he is elected president, that suggests he was the problem. He's got the bayonets. Jeff Davis does too. Before the US Congress can do something stupid, like being reasonable, the war is on.
Slavery (actually racism as practiced in various parts of the US), was the primary cause of political friction. But it did not cause the war. A settlement might have happened had the president not had the clear power of the military. Heads might have cooled , people maybe come to realize what was happening. Confirmed slavery advocates (not many), and Abolitionists (not many), might have been shut up. People could have dealt with slavery honestly. That had not been tried before. I don't think there were many in the US that wanted slavery to continue, but the screaming and yelling had deafened and silenced them.