You might enjoy reading 1491 and learning more about the cultures of the Americas. There is way more there than "tech from 1500 BC", and I don't feel like just quoting from the book because I want people to go read it.
It is important to realise that there are recent estimates that mention 9 out of 10 people all over the Americas dying of diseases. Remember that diseases travel faster than European invaders, so by the time they arrive at those locations the population is already in kind of chaos and traumatised.
There were a lot of people living in the Americas. A lot. The first chronicles mention large cities and populations, other chroniclers passing the same regions some years later see nothing. In certain areas, such as the Amazon, where people built things out of wood, almost nothing remains.
It is also important to remember than in many cultures, part of the healing process for a disease involved family and loved ones doing wakes and staying close to the afflicted. This causes a havoc as contagious diseases such as pox spread and claimed whole families, and then the next family, and so on. Pox was not common, nor was flu.
Many variations of pox are associated with use beasts of burden, most of the indigenous cultures didn't use them. So no resistance to cowpox, smallpox, etc
> I doubt that the indigenous Americans would have been able to adopt European technology fast enough to succeed in beating the Europeans back.
Please, read that book. You'll see the indigenous population of North America adapting quite fast to European technology to the point of managing sailboats. Also, sidenote the Spanish first met the Inca not on land but on the sea, they bumped into one of their large sailboats. Europeans adopting indigenous technologies in South America because theirs didn't work. This happened everywhere. Everyone was adapting.
Many of us learned different stuff in school and uni, mostly because it takes a very long time for research to trickle into school curriculum, and also because of the bias of those telling the stories who century after century create a narrative that favours them.
There a lot of recent research that throws away a lot of what was taught to me in school. Unfortunately, the usual reaction from people is that "this is not what I was taught, so it must be wrong!" and then proceed to repeat fairy tales about technology superiority which is a positivist way of seeing things that is very flawed.
"Beating Europeans back" is not the only possible outcome. It is not about beating people back to the other side of the Atlantic. If so many native people had not died of diseases, the Americas would look much different today.