The fellow who discovered America was a Viking named Bjarni Herjolfsson. It is estimated that he made his discovery in the year 986, centuries before Christopher Columbus "officially" landed in America, in 1692.
Around 10,000 years ago, at the tail end of the last Ice Age, so much water was locked up in ice that the Bering Strait was a land bridge. It is thought that men walked across from Asia, probably chasing game, settled and spread over time and became the Native Americans of North and South America.
The Norseman Bjarni Herjolfsson provided the first DOCUMENTED proof of the existence of the Americas, and literally "spread the word". The Native Americans did not discover America. Native Americans implemented their namesake: they inhabited the land, UNBEKNOWNST to the world.