Christopher Columbus is the correct answer because he is widely recognized as the explorer who discovered America. He embarked on his famous voyage in 1492, funded by the Spanish crown, and landed in the Caribbean islands, believing he had reached the East Indies. Columbus's discovery paved the way for European colonization and the eventual establishment of the United States of America. Marko Polo, Nikola Tesla, Albert Einstein, and Barack Obama are not associated with the discovery of America.