Horses were reintroduced by Spaniards, but precolumbian mobility was not what we'd call minimal today and adoption of horses in the plains was deeply tied to political changes from Spanish colonialism in the southwest. As one example, people would make annual pilgrimages hundreds of miles across the desert from modern Phoenix to the gulfs of California and Mexico. People in the Northeast would travel hundreds of miles on their waterways for social visits. There was a vast trade network spanning the continent from the arctic down to South America, and the Pacific to the Atlantic.
Epidemic disease also didn't spread in advance of European contact. The demographic shattering diseases that led to those (fairly questionable) population loss figures happened after sustained European contact. Some regional disease slightly preceded contact, but we think they were fairly minor events demographically. Textbooks and popular media haven't caught up with the new work in this area though, like: https://doi.org/10.7183/0002-7316.79.3.487
Horses were reintroduced by Spaniards, but precolumbian mobility was not what we'd call minimal today and adoption of horses in the plains was deeply tied to political changes from Spanish colonialism in the southwest. As one example, people would make annual pilgrimages hundreds of miles across the desert from modern Phoenix to the gulfs of California and Mexico. People in the Northeast would travel hundreds of miles on their waterways for social visits. There was a vast trade network spanning the continent from the arctic down to South America, and the Pacific to the Atlantic.
Epidemic disease also didn't spread in advance of European contact. The demographic shattering diseases that led to those (fairly questionable) population loss figures happened after sustained European contact. Some regional disease slightly preceded contact, but we think they were fairly minor events demographically. Textbooks and popular media haven't caught up with the new work in this area though, like: https://doi.org/10.7183/0002-7316.79.3.487