Final answer:
European diseases had the greatest impact on Native Americans during the Columbian Exchange.
Step-by-step explanation:
When the old and new worlds met in the Columbian Exchange, European diseases had the greatest impact on the Native Americans. These diseases, such as smallpox, measles, and influenza, were brought by the European explorers and settlers and had devastating consequences on the Native American populations. Due to lack of immunity, the Native Americans suffered high death rates and population decline.
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