If you actually bothered to read the Wikipedia link it would lead you to this article, “Russell Thornton estimated that by 1800, some 600,000 Native Americans lived in the regions that would become the modern United States and declined to an estimated 250,000 by 1890 before rebounding”
350,000 dead from that short period, but that came after the mass colonial genocide in the Americas, where the population of “Indigenous Americans is estimated to have decreased from approximately 145 million to around 7-15 million between the late 15th and late 17th centuries.” Assume 90% of that is from disease, that’s 13 million killed.