I'm not sure how you would expect that civilization to survive prolonged contact with the Apache, Comanche, Aztecs, etc.?

As with everywhere, the indigenous peoples of the Americas had a wide variety of different cultures, including some that were highly aggressive and others that were more peaceful; some that were very hierarchical and others that were more egalitarian.

For example, in Africa, the Nok were comparatively peaceful (it's not known what happened to them); the Kushites not so much--they conquered Lower Egypt and held it until the even more aggressive Assyrians drove them out in the north and, eventually, they fell to aggression from the Aksumites in the south.

China provides multiple examples of times of comparative peace and harmony, and times of aggression and war: back and forth, over and over, throughout the centuries. The Jains were almost pathologically peaceful.

And so on.

I just don't see how history provides any support for the idea that you can "slowly work towards a system free of exploitation" given all the instances of shifts back and forth in degree of exploitation.