In summary, his new book 'The Dawn of Everything' tries to present evidence in a more scientific way in order to destroy these inaccurate portrayals of primitive societies.
I even tried to start a thread and discuss the book in this HN post, feel free to participate. https://news.ycombinator.com/item?id=30002793
No doubt that's likely very true (as archeological evidence now suggests it is). However, it seems to me that Rousseau took his more simplistic view as a hypothetical starting point to argue his main one - that of the Social Contract.
He probably reached a larger audience with his small book than grinding it fine by including unnecessary details - just guesswork on his part - about archeological prehistory, of which hardly anything was known in the 1760s.
As it was, Rousseau was influential as witnessed by events in 1789. Some would even argue that he was too influential.
And there was plenty of warfare in North America pre-Columbus. Iroquois had a long reputation as a ferocious warrior culture.
This all ultimately ties into the question of whether the notion of linear progress (i.e. that you can order all the possibilities on some scale from less to more progressive, and that history broadly evolves from the former to the latter) is even applicable to sociopolitical development at all. Until fairly recently, that premise was pretty much taken for granted.