What happens IF a christian that isn’t really a christian leaves a church?....
Actually nothing..
I Peter 4:17.
Many small nondenominational (not leftist) churches are being formed coast to coast.
The leadership in many churches started buying into liberal BS in the last few years and have lost their way. My wife and I are looking for a new church because of this.
"Culling the herd" -- that is, becoming a smaller but purer minority -- means you'll have less of an effect on the country, and probably that the rest of the country will be less well disposed towards you. If you feel like Christians are isolated or disliked now, wait until "nones" and atheists become a majority.
Progressive: one who is in favor of progressively screwing up the once great United States of America
Plenty of folks who are sincere Christians still belong to apostate mainstream Protestant churches. They just ignore what is happening to their denomination in the belief the pendulum will change some day.