The crusades had an indirect impact on the discovery of America. The Fourth Crusade which resulted in the sacking of Constantinople (1204) resulting in the fatal weakening of the Byzantine Empire. With the eventual fall of Byzantium to the Ottoman Turks (1453) and the collapse of the Mongol Empire to the East, Europe's access to China and the far East was lost with the disintegration of the Silk Road.
The crusades had another indirect impact upon the discovery of America. As a consequence of the crusader contact with Islamic civilizations of the Middle East, Europeans of the Dark Age were again introduced to cultural, scientific and mathematical advances. This knowledge would contribute to Europe's own eventual awakening in the Renaissance and Enlightenment.
In addition, the crusades introduced Europeans to spices and fine goods from the East. With access blocked to these products upon the loss of the Silk Road, European sought another route to the East. After experimentation around Africa by sea proved arduous, Columbus' own voyage to circle the globe was a product of learning and desire for discovery initially brought about by the crusader's contact with the Middle East.