The separation of church and state in the U.S. constitution is more honored in the breach than in the observance. Those who want to escape from organized religion must fight for that freedom against those in power who would foist religious views upon them at every turn. The religious Pledge of Allegiance continues to be recited in public schools, despite its being clearly unconstitutional.
Religious oppression is far worse in other countries than it is in the United States. Living here is not like living in an Islamic republic, where rejecting Islam (apostasy) is punishable by death. Still, that is a very low bar. Countries that lack religious freedom have a very bad quality of life in other respects, as I pointed out in my book Why Atheism Will Replace Religion.