Obama may want everyone to believe that the United States is not a Christian nation, but no one can successfully argue that it didn't begin as one! Freedom and liberty are clear biblical concepts. That realization, and the desire for every American to be able to worship according to his or her conscience, is precisely why our country has been the most tolerant toward so many different religions, even those that believe it is an honor to kill Americans.
"In Touch Ministries" recently televised a lecture by David Barton, founder of Wallbuilders ministry, titled "Is America a Christian Nation?".
Barton presents REAL (not manufactured) evidence from original historical documents of the founders of the USA. The truth is that most of the founders were Christians, not agnostics, not Deists, not atheists.
You can watch the lecture at the link below. Not sure how long they will keep it on their home page, but it can also be purchased. The second link is the Wallbuilders website, with info on revisionist history, real history, and other resources.
As any historian knows, you always have to go back to the original sources!