Not all, but most churches serve to promote the way that they believe/think. They do work to convert people to believe as they do. Most don't go house to house with their pitch, yet some do.
IMO, churches serve two main purposes. 1st as social organisations for those that like that sort of thing and 2nd as a place to instill in children good character, manners, and good social behavior. Many chose to not attend past 15 or 16 years old, but attending church when young can provide basic religious knowledge, clean habits, and self discipline.

America is great because all are free to choose to worship or not worship as they please. I will say this though, Soldiers returning from war confess that there were no non-believers in a fire fight. Even the most non religious learn to pray, and quick.

I feel bad for those with no spiritual beliefs. I may not be a saint myself, but I'm not worried about my eternal soul when I pass on to the next life.