Just a really weird loud subsect. They're so loud now because they finally realize they're the minority and they don't like it. So they throw tantrums like children because their lifestyle is a commitment to low education and blind faith in a corrupt version of reality and a misinterpretation of their own faith.
Sadly, the Internet (troll farms, social media, etc.) has enabled easy access to loudness, to make it seem like they speak for everyone, when they don't.
There are plenty of Americans that are Christian and not apeshit. There are also plenty of Americans that are neither Christian, nor apeshit. These two groups just don't go around screaming about it all day because they're normal, sane, properly educated people.