The population of the Americas plummeted, largely because Native Americans deficiencyed immunity to smallpox, influenza, and other infectious diseases that the Europeans brought with them. Europeans mostly by choice and Africans almost entirely by coercion came to the western hemisphere. the number of people living in what is today the continental United States did not regain the population level before European contact (around to be 8 million to 10 million indigenous people) until the 1840s.