The first and second waves of Eurasian immigrants resulted in the First Nations. The first invasion came into Alaska and worked its way down the west coast, deserts and mountains. The second wave came over the Atlantic Ocean and has been found as far west as Minnesota. Both of these originated in Turkey and the Baltic nations, but DNA differs enough to track them. It is possible that these immigrants brought the practice of slavery with them.
As far as we know, the next arrivals were the Vikings. Leif Ericson is said to have followed the directives of Icelanders who had sailed west far enough to spot land, but then returned. If this was during the last ice age, as some hypothesize, the Vikings could also have been directed by sailing south of the ice and by consulting their “sunstones.” https://phys.org/news/2011-11-viking-sunstone-myth.html
We know that Vikings dealt in slavery because slave markets have been found, including a large, active one in Ireland. But if they meant to enslave the Americans, they probably quickly determined that negotiation was the best policy. The Vikings were vastly outnumbered. Their widespread villages did not survive.
We think Christopher Columbus arrived next. Ferdinand and Isabella, his sponsors, were very clear: the inhabitants were to be Christianized and remain free. Columbus was under the authority of the crown, as would be all native inhabitants. Later the monarchs amended the instructions so colonists could require labor and tribute, supposedly to correct reported laziness.
But greed got the better of Columbus. When the king and queen heard of his enslaving and mistreating the Native Americans, they sent a ship to relieve Columbus of his governorship and bring him back in chains.
It was this protection of native inhabitants that forced European colonists to turn to Africa for slaves. They were not the first choice. So much for the anti-black racist argument of slavery.