If the Ottoman Empire had not captured Constantinople, how might the exploration of Africa and the Americas have been affected?

The search for sea routes to Asia was already going on in advance of the fall of Constantinople. The Atlantic-facing powers of Spain and Portugal were determined to cut the middlemen out of their trade with the Far East and become new masters of the importation of silk and spices. While complications in east-west trade were posed by the fall of Constantinople, that event did not choke off that trade. Europe continued to import goods from the east at slightly higher prices and with temporary interruptions through Ottoman (rather than Byzantine) Constantinople and without interruption through Mamluk Egypt.