No empire in the world would have been able to accomplish what the Spaniards did if the indigenous population of millions decided to put up a strong resistance against them.

The 2014 Ukraine invasion worked because the nation was splintered and demoralized, and the Russians could just roll in and take what tey wanted. The 2022 didn't because the Ukrainians were unified and willing to fight, despite a much higher degree of military readiness on the Russian side.

But going back, over time, the native population became serfs, picked up the language, culture, religion of their conquerors, they even intermarried to a significant degree. Latin America is full of people with both European and native ancestry to some degree.

Yes they were serfs, but so were most European peasants at that time.

And only a couple hundred years later, as the Spanish empire collapsed, these people, culturally Westernized at this point, threw off the yoke and formed their independent countries, with Mexico starting it's own empire.

I just cannot imagine a credible scenario in which even if Western colonial powers didn't manage to conquer the territory of Mexico, they wouldn't have been Westernized to a significant degree, by the Aztec rulers themselves starting a Meiji style modernization.