https://www.arizonachristian.edu/culturalresearchcenter/research/These folks have been polling American's worldviews for a while, and the results keep trending downward. Many Americans say they are Christian, but asking them what they actually believe reveals usually a buffet mentality, picking stuff from Christianity and other belief systems to create a "plate" they are happy with.
Actual Christianity is definitely falling off in America. Just look how many churches are flying rainbow flags and not being abandoned. Jesus said "many are called, but few are chosen" and “Not everyone who says to me, ‘Lord, Lord,’ will enter the kingdom of heaven, but the one who does the will of my Father who is in heaven." We are seeing lots of that here.