Columbus did not discover America. When Columbus arrived in Hispaniola in 1492, he found the Taino people already there. If he would have gone to a neighboring island, he would have found the warlike Carib tribe, and Columbus would not have survived to have made his claim. There were significant cultures already existing in the Americas. The Aztec and Inca Empires were quite powerful in Central and South America, and the Mayan civilization had already gone through its golden age and collapsed. In North America, various tribes had already existed for generations and had their own complex cultures. Historians are continuing to learn more about the cultures that existed in the Americas before Europeans arrived.
Columbus was not even the first European in the Americas. That honor belongs to the Vikings, who had small outposts in Canada. These were not permanent, and they soon collapsed as the Vikings left raiding for agriculture. Columbus's main claim to fame was claiming the Americas for the Spanish and thus beginning Western Europe's colonization frenzy in the Western Hemisphere.