Trust me when I tell you that it is not very popular to be a Christian anymore it seems so I would not think anyone would "fake it" to "fit in."
Are you fucking kidding me?! You only have something like 80% of the US population, all the prior and current presidents, 98% of the politicians, most of the news reporters, most of the school teachers and administrators... This country is
steeped in religion/Christianity. Christmas decorations go up in October, all the religious holidays are very overtly celebrated, it's unthinkable for the president to not do any prayer or religious type of ceremony, those who point out that religious icons on public property are unconstitutional get persecuted and receive death threats... Atheists are the ones who are not very popular. Watch any news reporter interviewing an atheist. It's as if they are interviewing some weirdo with cancer.
Perhaps you are right. I guess my feeling is that many people call themselves Christian in this country but just because they say they are does not mean they actually live it like they should so I often questions those numbers.
That said, I do feel like there is a movement towards Christianity being less accepted, or popular, in our society than it used to be. This is my own perception of course.