It would have almost no effect. Unless the Americas were completely isolated from Eurasia, everyone would have died anyway. The Americas were not conquered by force of arms, but by disease. A common pattern: send an expedition, which discovers cities, towns and gardens. Send another expedition years later: find nothing. I highly recommend the book 1491, which is a great historical account.<p>There was absolutely nothing (short of complete isolation until the development of modern medicine) which would have prevented the Indians from dying out. Even if the Europeans did nothing but bring candy, puppydogs and fireworks in trade for furs, the puppydogs would have carried diseases deadly to American Indians.