Hello. I just saw in an AskReddit thread that American "Indians" didn't always live in tents, but had huge cities and other traits of developed civilizations. I've heard a lot about civilizations like Incans and Mayans, but never the people native to what we now know as the USA. The post also said that a huge percentage of them were wiped out by disease that spread from Central/South America and spread north, which I'd also never heard. Regardless of how accurate this is, I now realize I've never heard of (or even wondered about) anything regarding the culture of North American natives prior to Jamestown. What are some good sources to begin learning about them?
A perfectly appropriate starting point would be with Charles Mann's 1491. It is written for the informed lay person but it is about as good as it gets in that genera. See here.
While 1491 is a great book and one I would recommend in general, it might not be exactly what you're looking for. It's more focused on scholarship concerning the pre-Columbian Americas has changed over the years than what was actually going on pre-1492, though you do get a bit of that. Many if not most of its examples are pulled from Mesoamerica and South America, rather than what's now the United States, so again it might not be exactly what you're looking for.
As an alternative recommendations, I'd suggest Timothy Pauketat's Cahokia: Ancient America's Great City on the Mississippi or Ancient Cahokia and the Mississippians. WHen people talk about pre-Columbian cities in what's now the United States, they're generally talking about Cahokia since it's the most famous (and probably the largest) of them. Both books are good introductions to the topic, though Cahokia: Ancient America's Great City is a more of a general audience introduction while Ancient Cahokia is an academic introduction to the topic. Pick whichever seems appropriate to you.
You might also be interested in Knights of Spain, Warriors of the Sun: Hernando de Soto and the South's Ancient Chiefdoms. This book follows Hernando de Soto's failed attempt to conquer the American South for Spain, between 1539 and 1542 (with his men spending another year after de Soto's death trying to get back to Mexico). It combines history and archaeology to give you a look into what the region was like when Europeans first reached it.
And, of course, we have a lot of posts around /r/AskHistorians that could help you too. Here are a few that you might find useful.