There is one we can definitely rule out as not discovering America and that is Amerigo Vespucci, because he was the one who demonstrated that the landmass that Christopher Colombus discovered was not Asia but was actually a new landmass completely unknown to Europe. Now Christopher Colombus was the one who was credited with finding the Americas but Leif Erikson was confirmed to have made it there about 500 years earlier. It all depends on what your textbook says.
