Possibly the most dramatic, immediate impact of the Columbian Exchange was the spread of diseases.
European settlers brought many plants and animals from Afro-Eurasia to the Americas. It's important to note that before all this, the only domesticated animals in indigenous American communities were llamas and alpacas and some small animals.
To support their own settlements, Europeans also brought wheat, barley, rye, sugar, bananas, and citrus, among other crops—and this changed the economy.
Crops from the "New World" (the Americas, so not new to the indigenous peoples) revolutionized cuisines in the "Old World".
