It never would have been settled as it is now. The Americas would be much more like Africa is today

African slaves where brought over to the Americas because they had partial immunity to both European diseases and tropical diseased, whereas natives had no immunity to European diseases and died like files, so estimates putting the death rate in the first few years as high as 90%, and the Europeans fared no better with the average life expectantly less than a few years.

So with there partial immunity to both European diseases and tropical diseases Africans where the only people to survive more than a few years making them incredibly valuable as labours.

But without the incentives European powers had to get whites to migrate... Slavery was the only option. As horrible of a system out was.