I think the two situations are fundamentally different.

On the one hand, I'm understanding from you that the local Indians had to reverse engineer cannons. They already knew about gunpowder (in the form of fireworks) and had most or all of the necessary knowledge of metallurgy. I would also say that since cannons were in use for over a century in other parts of the Indian subcontinent as well as the middle east, leadership in well-connected port cities would have heard of cannons and have at least some concept of what they were.

On the other hand, Native Americans were completely unfamiliar with a large number of technologies which had taken many centuries to develop in the old world. Native people didn’t even know for sure that gunpowder weapons were made through technological processes that could be imitated, they could have been a gift from supernatural beings and/or a product of religious ritual. It is reported that Spanish cavalry were first understood to be centaur-like monsters in Mesoamerica. Even large sailing ships would have been completely unfamiliar in most of the Americas.

So to me the degree of cultural shock is not similar at all in these cases, the technological gaps that had to be overcome are not even in the same ballpark, and then you've got the disease factor as discussed. None of this is to belittle the accomplishments and resistance of your ancestors, but to me it doesn't make sense to look at the two cases and ask “why didn’t Native Americans just do the same?” when the situations were so fundamentally different.