The most accurate reason for saying that Europeans did not "discover" the Americas is that Native Americans were already inhabiting the land in the Americas.
Long before European explorers arrived, various Indigenous peoples had established rich and diverse cultures, societies, and civilizations across the continent. The term "discovery" implies that a place was unknown or uninhabited, which overlooks the fact that the Americas had a long history of human habitation and cultural development prior to European contact.
While there were earlier explorers from other regions, such as the Norse voyages led by Leif Erikson around the year 1000, the phrase is often associated with Columbus's arrival in 1492, which sparked a period of extensive exploration and colonization by European powers. However, it is critical to acknowledge the existing populations and their histories, which predate and were deeply impacted by European arrival.