Hmm… no great civilizations? As already mentioned the Mound Builders and Anasazi are two that we know of. But, there were other great civilization that you probably don’t know about because they didn’t build great temples. The Purépecha civilization built small temples, but their empire shared the border with the Aztecs and spread all the way across to the Pacific Ocean. But, the fact that they were great administrators instead of warriors or temple builders is lost on most.
Take a trip to Chaco canyon or visit some of the pueblos. Many pueblos people still live in the buildings constructed in the 12 or 13th centuries! No great civilizations? I beg to differ.