There weren't much colonies in 1536. Just the conquered Caribbean islands and recent victories in Mexico and Peru.
In 721, Iberia just got conquered by Muslims. I expect that some conquistadors will try and live in primitive France and Italy. Others will just try to live like kings in the New World and the Natives will slowly but surely retake their societies. 1536 is too early for the Americas to be massively transformed and become "westernized" and 721 Europe can't really do anything with knowledge of the Americas.
By 900 AD, history will be mostly back to "normal" with the tales of Pizarro and Cortes fading into legend on both sides of the Atlantic.