Final answer:
The introduction of European diseases such as smallpox through the Columbian Exchange resulted in the death of up to 90% of the indigenous populations in the Americas.
Step-by-step explanation:
The most detrimental effect of the Columbian Exchange on American Indian groups was the introduction of lethal diseases, leading to massive population declines.
European colonization and the consequent Columbian Exchange drastically affected the indigenous peoples of the Americas. European diseases, such as smallpox, measles, mumps, and influenza, wreaked havoc among the American Indians. Without any natural immunity to these illnesses, the mortality rate skyrocketed, decimating tribes and erasing entire cultures within a short span of time. The European pathogens were fatal, eradicating a staggering 80% to 90% of the native population in some areas. This not only caused immediate loss of life but also disrupted the transmission of culture and knowledge, severely impacting the continuity of indigenous societies.