I think I may have inspired this thread
I actually think that Aragon has a good chance in the new world if they have Navarre. Ferdinand apparently was the one who actually was gullable enough to believe Columbus about Asia, and later used that to take credit for discovering the Americas, so if he didn't marry Isabella, and managed to somehow inherit or conquer Navarre from his half sister Eleanor, he might still fund the Columbian expedition or some similar one to try to compete with the Portugese spice trade, since especially in the beginning the profits to be made in the spice trade were pretty insane. Even if he just ignores Columbus and any similar idea men, the Americas will almost certainly be discovered soon given how much the Portugese were beginning to sail in that general area with fully ocean going ships. It may take another decade, or even two or three decades, but it will happen.
As for their prospects once they get to the Americas, Aragon was more populous than Portugal, and with it's mediterranean Empire it would have a similar population to Castile, so they have a good shot in the America's. I think that where they end up once they catch colonizing fever is going to be kindof random, but the Aztecs and Incas are the two most prosperous civilizations in the Americas, so Aragon would probably want to conquer one or both of them for sure. If they totally miss out on south and central america, I could also picture them trying for lands in todays U.S., given their northern location. The Misissippi might be attractive, or maybe the Carolinas if they discover the gold there.