I think the introduction of livestock, and food had a very different effect on the Americas then diseases. We the livestock and food, the Americas was able to develop these product into there culture, like horses. Horses didn't originate in the Americas and the United States of America has one of the largest population of horses. As for the diseases had a very negative effect. With the Europeans having superior weapons and armor, then with the added effect of diseases deviated the Native American races that resided in the Americas; cut down their population by a massive amount.