pronouns - It is us? It is we?

Which would it be--it is us, or it is we?

"Who is the real culprit? It is us, the ignorant, apathetic people of America."

Or, "Who is the real culprit? It is we, the ignorant, apathetic people of America."

Or plural?

"Who are the real culprits? They are us, the ignorant, apathetic people of America." (Sounds more like the name of a retail store--They R Us.)