While the door has been cracked ajar there is still much to be done. Free expression of non-belief is a right afforded all Americans but mainstream America doesn't seem ready to accept it.

Mainstream America is made up of people who use christianity as a fallback point when anything is challenged.
Few find time to question their beliefs.
Many that do are now happily coping with life as atheists and more will be open about being atheists.
There is also a theory going round that many atheists are being forced into the open by the christian right and their current push for power.