A North American bronze age may have been impossible

First Nations get a lot of flack from detractors for being stone age cultures, despite being far more socially developed than Europeans when they first arrived.

But I have been wondering why all technological innovations happened within the framework classified as the "stone age". Even in places where cities were built, like Cahokia, it was all with stone age methods.

For the First Nations in what is now Canada, I think I have found the answer:

There are no significant deposits of copper and cassiterite (the tin used in bronze) existing in the same geographic region. There was no way to stumble upon making a bronze alloy because the necessary ingredients did not exist near each other.

The only exception is a modern mine in Kemptville, Nova Scotia which contains tin, copper, zinc, and gold — but requires modern machinery to access those metals.

As a disclaimer, my research so far has been rather amateurish. I also haven't started searching to see if the same situation was true in the US or Mexico.

But my tentative hypothesis, at least for the nations up in the north of Turtle Island, is that a bronze age would have been impossible.