Ok, here's the scenario: People are scheduled until 11:00. We're not necessarily finished with everything at 11:00 so our boss makes us stay past. No one wants to stay past 11:00, but we are told by our boss that if we leave, we could be terminated for job abandonment. Even though our scheduled time to leave is 11:00.

Somehow this doesn't seem right to me. I can only assume there's some sort of law or something protecting employees from something like this, which would seem like wrongful termination. Am I wrong?

Yes, you are wrong. There is no law protecting "scheduled" time. If the boss says you stay beyond the time scheduled, you stay beyond the time scheduled. Mandatory overtime is legal in all 50 states. If you are fired for refusing to stay, that will NOT be a wrongful term, but entirely legal.