Why weren't there any pre colombian empires in the modern day USA?

We had a similar question a few days ago. There are a couple of responses, there, but probably not the ones you're looking for.

This is an exceptionally difficult question to tackle. In order to answer why something didn't happen, we need to know why that thing does happen. Why do empires rise in the first place? Until we know that, we don't know whether or not we should expect one to arise within the pre-Columbian USA. We'd also need to know what exactly an "empire" is, there's enough flexibility in the world that historians can write books like The Ambiguous Iroquois Empire and The Comanche Empire (both post-Columbian phenomena, though with pre-Columbian roots).

You also need to know what did happen. There's still a lot we don't know about the pre-colonial America, which makes this question doubly challenging. We could talk about archaeological cultures like Poverty Point, the Hopewell Interaction Sphere, and Cahokia, but there are significant gaps in our understanding of their political structures. There are also historic polities to consider. Would the Calusa's conquest of southern Florida count as empire-building, even if they're generally considered a "chiefdom" rather than a "state"? How about Quigualtam, with its ability to command the military of the entire lower Mississippi valley, a deploy hundreds of war canoes, some of which carried 70 men each? How about Coosa, sprawling some 300+ miles along the southern Appalachians?

We'd really need to get into the details of these questions before we can decide would call any of those empires, or whether your question is less about the semantics of what makes an empire and more about the general nature of the polities that were present at the time. I don't want to get too distracted by this particulars yet until I know about what you're really looking for.