The way that American conservatives use religion without really believing anything in it is an aberration throughout most of human history.

I'm not convinced that's true. The powerful have always used moral codes and laws selectively and misogyny has been dominant throughout history(there are exceptions, of course). Also, I don't think the American conservatives "don't really believe in anything". I think they are held together by beliefs and feelings, regardless of whether their beliefs have an actual foundation in their religion. I think they they believe it does.

But that's the fundamental problem with belief systems, it's whatever the believer believes it to be. If someone hears something on Fox and thinks it comes from the bible, it's a religious belief and is now a part of their religion, even if it contradicts their stated religious belief from 5 minutes ago.