I think even an amateur historian would find indisputable evidence that America was founded on Christian and Biblical principles. A truly tolerant non-believer would accept that reality and not raise hell about the various Christian symbols, traditions and influences that are ingrained throughout the American system of governance.
To remove all vestiges of Christianity from the state would rip the heart out of what has made America the most enduring and shining opportunity for freedom, liberty and prosperity in human history. Instead of the utopia that atheists suggest it would create, the truth is that it would be hell for everyone - even those who don't believe in heaven or hell.