I see your point. The "greatness" is very subjective. I assume you don't want to just tell kids "we're great", but give them reasons to think so (e.g. due process, Bill of Rights, etc). If you teach civics, and history, you can let the kids decide for themselves. Slavery is a stain on this nation. But we ended it, passed the Reconstruction Amendments, and have slowly been improving. Are we done? Certainly not. We have come a long way, but we still have a ways to go. Teach all of that. Not that slavery helped the slaves (which is the latest drivel I've heard from the right recently).

Jefferson is a great example. He was a slave owner. He was also a principal architect of our nation. Kids need to know both of those things. And he was not inspired by the 10 Commandments (nor was Thomas Paine, or Madison, or anyone else). Teach the facts, good, bad, or neutral. But also teach how these influenced what we see today. History is about more than names and dates. We are where we are today because of past events, and we need to understand those events.