I am sure that you mean “Norse” and are referring to Leif Erickson, a Norse explorer who is believed to have established a Norse colony in what is now Newfoundland, approximately 500 years before Columbus (who, by the way, never landed anywhere in North America). Erickson was not, however, the first to visit the New World. That honor goes to Brendan of Clonfert, an Irish monk who visited North America some 500 years before Erickson – who by the way knew of this (as it was mentioned in many Scandinavian stories) and referred to the lands south of his Norse colony as “Irland it Mikla” or “Greater Ireland.”
Since Brendan was a monk, you are correct in assuming he brought his religion with him, but he did not enslave anyone, nor did he bring any plagues with him. Slavery involving North American Indians actually began among the Indians themselves. Slavery was a common practice among the North American tribes, as they often enslaved members of rival tribes, and when Whites began to settle in North America, the Indians took White slaves as well. This is not say that Whites did not take Indians as slaves because some did. But the idea of slavery, the practice of slavery was not introduced to the Indians by Whites.
And as far as a peaceful nation, nothing could be further from the truth. The notion that Indians were a peace loving, everybody-gets-along-with-everybody group of people is utter nonsense. What do you suppose happened to the original inhabitants of North America? No, I do not mean those Indian tribes who were here when the Whites arrived. I mean those who were here when those Indian tribes arrived. Because, you see, the Indian tribes who were here when the Whites arrived in North America were not indigenous to this land, and when they arrived, coming up from South and Central America and Asia, they encountered the original inhabitants of North America, and in many cases they simply exterminated them. In fact, archaeological discoveries and Mitochondrial DNA research indicate that the original inhabitants of North America were Caucasian, arriving here roughly 8,000 to 10,000 years before the ancestors of the modern North American Indians made their way across the Bering Strait land bridge or up from South America.
Professor Dennis Stanford of the Smithsonian and Professor Bruce Bradley of Exeter University, both prominent and well respected archaeologists, have presented evidence that indicates ancient Europeans known as the Solutreans crossed over to and settled on the eastern coast of America from the Iberian Peninsula of Europe (where modern day Spain, Portugal and France now are) during the Ice Age.
In addition, the idea of “white” Indians is not something new, as they have existed for some time. The most well known of the Caucasian Indians are the Chepu Tule Indians, the Guanche Indians, and the legendary Madoc Indians. Pre-Inca skulls have been found in Peru with blonde, red and brown hair. Inca and Mayan Indians both have stories of blonde haired and bearded tribes that existed before they did, and who were killed off by the Inca and Mayans. Also, let's not forget Kennewick Man, a skeleton discovered in Washington State that has been dated to about 9,000 years ago, and whose DNA has been tested and found to be 100% European. And Kennewick Man is not unique in that ancient remains have been found in the United States from Ireland, Iberia and Africa. Not as old as Kennewick Man, but ancient nonetheless.