IMO secretly almost all have doubts.

I was a military brat... Mostly east coast, some Italy, then my folks retired to Missouri.
Seems most Catholics like in Italy are always asking for forgiveness... Like they know they aren't quite good enough.

Most of the folk I knew on the east coast were pretty 'whatever' about religion, but I was in Virginia and North. Not the Carolina's, and South.

Missouri was the first time I saw distinctions between Catholics, Baptist, and Pentecostals... Baptist think everyone is going to hall, Catholics drink enough beer, they agree. Pentecostals girls don't go to college, They marry an older guy in the church after HS and reproduce. Freaking weirdos all of then!

St. Louis and Omaha seemed secular to me. I don't recall a religious vibe from any neighbors or co-workers.

Then Texas, where there is a distinct portion of the population that refuses to change their mind. Homeschoolers because homosexuals that teach in the public schools. Open racism and hostility towards others over religion or a lack... And being Texans, they are right and that's it. Screw facts, evidence, whatever. Changing your mind is a sin. In fact Governor Perry probably outlawed changing opinions during his term in office. They know what they know and are completely confident they are right and others are wrong.