Newcomer here! Finished like 5 minutes ago from catching up with this TL, and i must say it's very well made, with the writing style synchronising surprisingly well with the content turning the bigger chapters into compact and interesting groups of information (i.e not tiring text-walls). Now i'll be entering discussion
The Incas and the Aztecs were not the only American civilizations that the Europeans could encounter. At the time of Columbus, there were
cities on the rivers of the Amazon rain forest, most notably the Tapajós River, and large tracts of the forest were cleared for farming via Amazon
dark earth that they create themselves.
Pre-Columbian Amazon Basin was
pretty densely populated btw, throughout the entire Basin could be probably as much as 100 million people at most, and half that at least, what would turn the region as the american counterpart to India. Although it must be left clear that the region wasn't homogenous, having three main influences plus foreign influences on the Basin's frontier (like Peru).
The Muslim control of access to India and beyond in the Middle East wasn't the only main reason for the European shift to the west, especially after the fall of Constantinople. Another reason is those Italian republics, especially Venice, gaining exclusive control of access to the Middle Eastern markets, charging exorbitant prices on non-Italian merchants to trade there. When Venice managed to get the Ottoman Empire to give it an almost exclusive trade deal, Genoa had to look elsewhere and western monarchs encouraged that. This is why so many of the earliest explorers for Portugal and Spain turn out to be Genoese upon a closer look.
Genoa and Venice had a fierce, and often antagonistic, rivalry reaching back centuries.
You can avoid this by somehow (because you have to solve the problem of the Arno) maintaining Pisa as a viable competitor, the downfall of pisan influence resulted in a dualism that really put the eastern trade routes to be dominated by one or other, if ya have the three (or if somehow possible, even more) competitors in the eastern trade, the OTL push for new trade routes that resulted from venetian monopoly (that was what effectively happened after genoese complete decline in the aftermath of the War of Chioggia) won't be there, other than that case i agree that western exploration probably won't be significantly altered from OTL. Another thing i would like to point out is that genoese-venetian rivalry was nearly always there, before Meloria, the venetians usually allied with Pisa against Genoa, and if you maintain Pisa as a viable player, the scales might be too much over Genoa (resulting in them being pisa'd) and then the dualism turns into Pisa-Venice, dualism that can turn both into the Genoa-Venice OTL rivalry or an effective oligarchy between the two, both ensuing in the push for new trade routes.
When it was announced that the Portuguese found a way to India around Africa and proved it, Venice panicked and thought of making a deal with the Mamluks of Egypt to redig the Canal of the Pharaohs. That plan was mooted by the Ottoman conquest of Egypt.
Venice actually tried to help the Mamluks in the fighting against Portugal, the venetians even trained the egyptian sailors fighting in the Battle of Diu and after the Ottoman conquest tried (and succeeded) to push Selim I into continuing the conflict with the portuguese, but these plans were destroyed at first by the not-conquest of Persia by Selim I and by the sudden death of himself.
By the way, I'm not sure about the Reconquista managing to complete its goal in Iberia so quickly and so early. IOTL, the Reconquista was an extremely difficult back-and-forth slog. Al-Andalus fragmenting into the Taifa states made it much easier, which was why the Andalusians desperately appealed to the Almoravids and Almohads to come save them even though those empires were religiously fundamentalist and thus antithesis to the Andalusians' comparatively liberal and urbane culture. For a Reconquista to be that successful, the following needs to happen: (1) the Christian kingdoms would need to unite, which is difficult when we consider the disparate ambitions among the Christian nobility and royalty as well as Andalusian efforts to fan the internecine flames (they knew a Christian union or alliance wouldn't be in their interest); (2) Al-Andalus falls apart into feuding taifa states; (3) no chance of a powerful Maghrebi state existing and coming to their rescue; (4) the Maghrebi peoples are seriously distracted away from the Iberian Peninsula--since they were more numerous than the Andalusians, they were a main source of mercenaries and slave-soldiers for Al-Andalus. Perhaps your hint of a future Christian invasion of North Africa could provide that, but IOTL, King Roger II of Sicily attempted that and maintaining it was an up-mountain struggle.
IOTL the Reconquista nearly restarted all over after Granada managed to be independent, as the Marinids tried to cross over in Iberia, but they were defeated and any other attempts (that they wanted to) were silenced by the Late 14th Century instability in Morocco. IMO, Reconquista isn't really a given, especially as it depends equally in Iberia and in North Africa, as an powerful berber state always went to secure dominion over the muslim territories in the Peninsula. The thing about any christian dominion over North Africa is that by now, apart from the coastal urban centres, the majority of the region is composed by nomadic tribes that are
ridiculously rebellious, and were pretty hard to control if you wasn't one of them, any christian attempt to secure North Africa outside the occasional italian port-city colony would be frustateously expensive and pretty non-rewarding, this if they manage to overcome all the hardships and in fact, do it.
Something i would like to point out is that, once Egypt is conquered by the crusaders, we could very well see the italian republics
going to the Indian Ocean to do trade, as they certainly won't be pleased by having to work with muslim middlemen, what could result in italian port-city colonies in the egyptian Red Sea and european forays into the East, what would be completely awesome to see by itself.