The US was founded by entire colonies of people coming overseas to worship the Christian God freely. Many key founders were deeply religious; believing all forms of government are doomed without the help of the Christian God. The Christian God was a huge factor in government and repeatedly credited as the guiding force and inspiration for the entire endeavor.
Christian prayer and Bible reading was a public school item until the mid 1960s. Church and state separation was entirely redefined around then as well; it didn't mean back then what people think it means now. The ten commandments was in courthouses. There are people still alive today that were led in prayer to the Christian God every single day of public school (and required to read the Bible); they're everywhere.