I agree they were almost all barbs by the time they had to fight off the colonial powers, but when the first explorers arrived they were still quite civilized. Most of the primitive peoples of the western hemisphere are the descendants of societies that were quite advanced in some ways. The quality of life in most parts of America was significantly higher than in Europe.
Some natives of newfoundland refused to allow the first known Europeans to land, for fear of disease, but traded with them over long ropes. The first people from this region ever taken on board an explorers ship was found to posses a silver ring and a sword with the mark of a known Italian craftsman, implying that the Viking-era journeys between the continents may have never really stopped, meaning they interacted with Europe on some level for centuries.
The main reason that north eastern native americans were typically seen is primitive is that their governments were not oppressive enough to force them to construct great works. Their huts still kept out the rain better than european houses, were warmer, and the average diet had about 1000 extra Calories, and were more nutritious. Their longbowmen were able to shoot arrows strait through plate armour and a foot of wood from over twice the range of any contemporary firearms. Most of the eastern US was only lightly forested when the first colonist arrived (wide enough spaces for large carriages to travel), and was kept in such a way as to funnel the wild game through specific paths through paths, while allowing some farming in the woods.
There is evidence that the primitive slash and burn farmers in the Amazon today are descended from a prosperous society that planted the jungle. Yes, much of the jungle is made of fruit orchards gone wild. While the region has horrible soil, some parts have been fertilized with a mix of charcoal, pottery chards, and other things, to the point where such places are more fertile than any modern fertilizer could make it. Of course, these people knew no metal working, so they weren't advanced in all ways.
The Hopewell culture had petroglyphs that they carved in the land (like some south americans did) with remarkable accuracy, although they can only be seen from the air, and also seem to have used such symbols like hieroglyphs for other writing purposes. Many American tribes were on the verge of inventing writing, already having ways to record genealogies and such.
Southwestern Indians built many large desert cities out of stone, often carved from cliff sides, and connected then with excellent roads. Many of these settlements had water collection systems making desert agriculture possible. Actually, many roads and settlements were more for religious reasons than anything else. The roads aligned perfectly to solar and lunar calenders. Their greatest road seems to go due north towards nothing.
The Mississipians had several cities and many, many significant towns. De Soto said that for much of his journey they were always within sight of some settlement. The more towns probably clustered around the Mississippi than almost any european river. (it is likely that he introduced disease and more importantly pigs around this time. Pigs spread disease and quickly devour the native crops leading to starvation)
Essentially all the crops domesticated in America were more nutritious than any old world crops, but the crop yields were lower. It seems that almost all old world crops are descended from the same originals, while almost every American tribe domesticated their crops from the wild forms. On the other hand, most old world societies borrowed their crops from others, but domesticated their own animals. Contact with these animals lead to many contagious diseases, and to immunity to such diseases. These diseases where far more devastating to those with no genetic or acquired immunity (plus, NAs had far less genetic diversity, so diseases could easily decimate communities. There is also evidence that often, when a few family members of the Inca and other native american civilizations died, the others chose suicide)
Most the plains Indians were probably descened from the Mississippian and southwestern desert city-dwellers. America had many true civilizations, but the sad truth is that the most civilized societies are not the hardiest when faced with new crises. The problem with these is that they collapsed before we could find out their real strengths, or before we could identify a single leader for most of them.
Also, while the Zulu were not advanced, there were much more deserving societies in Africa
- But we might just want that because we live here, whereas Poland has several good reasons to get into the game... blablabla 
