What if Portuguese monarch John II had initially agreed to fund Columbus's voyages to the Western Hemisphere?
Portugal would certainly conquer the Caribbean like the Spanish did. One butterfly is that if they decided to attack the Aztecs and fail, we could see a surviving Aztec Empire.
For how long? Disease will still do its thing.
Mesoamerican population fully recovered from Old World diseases in 20th century, 400 years after contact with Europeans.True, but if the Portuguese go in and utterly fail an expedition by a European power would probably not be launched for at least a decade. By then the Aztec population will have recovered somewhat, they will have guns and horses, and they will still have numerical superiority considering the logistics of getting an army from Europe to Mexico in the age of sail.
And even then, that was after millions of European immigrants colonized the land.Mesoamerican population fully recovered from Old World diseases in 20th century, 400 years after contact with Europeans.
And even then, that was after millions of European immigrants colonized the land.