They were too busy killing off one another during expansions and migrations, due to population booms as well as having fouled the previous nests (both of these have been common throughout the world; it’s repulsively racist and baseless to claim Precolumbian populations were immune), and climate change, which is 100% natural 100% of the time.
It is amazing that some destrudo kept them from establishing the type of civilization that could have supported such an essential tool, in what was clearly a land of plenty.