Interesting thought. Consider that slaves had never been brought here. Considering that they were captured and sold by other tribal Africans, they likely would have been sold to somebody else, or just killed. But either way if they had not been brought here, there would be no descendants of slaves here either, probably no Al Sharpton, Jesse Jackson, maybe not even a Barack Obama. So would we have been better off?
Depends on the metrics and who "we" is.
Economically, especially in the early days of the nation slavery was a valuable financial institution, especially in the more agrarian south (but significant parts of the north). This at a critical time in a start up young nation.
It was in many ways antithetical to the founding ideals of this nation, but I do give some leniency in remembering the times. Slavery is one of the oldest institutions of man and remains in practice in parts of the world even today. The fact that it was ended in the US in less than 100 years and at enormous cost to Americans is admirable in my view.
Culturally, both blacks and whites have been both harmed and helped. Its notable that the US ended slavery and yet lived amongst these former slaves, historically most of the time when slavery was ended it was because slaves revolted and took over (think haiti) or slaves were expelled from the nation.
Here that did not happen-and it certainly contributed to racial tensions (though not all slaves were black). Certainly, more slaves were taken elsewhere besides the US (brazil, carribean, and much more so the Middle east, where most did not survive and were not highly valued)
But also, blacks benefitted from slavery in the US-conditions here have always been better than africa, and slaves that returned to Africa (sierra leone and liberia) did not tend to do much better than other africans (certainly not better than the US). When I was in school a nigerian classmate (former marine, US citizen) told how she always dreamed of coming here, and how much better it was here, my african american classmates were actually hostile towards her, as they didn't see any benefit to living in the US. That created some tension I made note of.
So in the end, its a mixed bag for everyone involved. Its water over the dam, and I think we are better served by working together to make things better. I do not see modern identity politics as helpful in this.