I'm convinced secular society is going to die out and basically reset itself while the devout Christians continue to survive and thrive since they don't have to deal with any of this nonsense for the most part. In 100-200 years after the collapse/civil war/apocalypse, whatever remains of the United States will be a predominantly Christian society based on strong values and hard work, much like America 200 years ago. The significantly higher birthrates among devout Christians alone practically guarantees this.