Ga wb,
That's a difficult question. It'll take some thought but I can see a very good discussion coming out of this.
Quick first thoughts:
1. We are worse in the area of loss of state and individual rights.
2. We have not, nor would we ever have had, the same government after the war as we had before the war so the 630,000 deaths accomplished something. IMO those deaths accomplished a much worse form of government that was intended by our FF's.
3. Westward expansion would have happened no matter. Did it benefit from the War? If so, would the Indian population have fared better with a slower migration of Europeans westward and did the war speed that migration?
4. As you noted, the physical, emotional, political, sociological, financial trauma that it caused the nation reverberates to this day. We would have been better off in each of those areas without the conflict.