Apparently, at least one American Indian was brought back to Iceland by the Vikings.

Via: http://news.nationalgeographic.com/news/2010/11/101123-native-american-indian-vikings-iceland-genetic-dna-science-europe/

Five hundred years before Columbus sailed the ocean blue, a Native American woman may have voyaged to Europe with Vikings, according to a provocative new DNA study.

I assume some novelist will get ahold of this soon and write the book!