The existence of a church does not signify that god is real. I get that. But is religion real? Even though it is based on a falsehood? And if not, then why build a church? And what makes such a building a church? Thus with governments: why build a prison? And why do, and how can prisons exist if there is no actual authority?
If a prisoner accepts the premises that you suggest, is that prisoner then free? Or is he still subject to that authority (illegitinate as it may be) and unable to leave the prison?