These are the 3 main reasons I think native americans were considered primitives: lack of metal tools (some groups had access to copper and bronze, but none had iron), lack of any sort of writing (writing didn't extend much beyond central America) and, especially in the warmer places, wearing little to no clothing.

Still, no one in their right mind would ever look at the huge temples and cities built without animal traction and think "Yeah, only a group of primitives would do that". I mean, when you look at the megaliths of Sacsayhuaman, you immediately think "How the fuck did they do it?"