In his inagurual Adams was assuring people that he would not discriminate against them because they were Christians. Nowhere does he either say "I am a Christian" or "this is a Christian country." He just says "I respect the religion of people who call themselves Christians, and if that helps to make me politically acceptable, then I am happy to serve."

Adams was a bit unusual, in that he called himself Christian in the sense that it was often used at the time: "civilized and moral." But he did not believe, for example, in the divinity of Christ, making him not quite what modern Christians would call "Christian."

More quotes from Adams about Church and State, the bible, etc.:

"Checks and Ballances...are our only Security, for the progress of Mind, as well as the Security of Body. Every Species of these Christians would persecute Deists, as soon as either Sect would persecute another, if it had unchecked and unballanced Power. Nay, the Deists would persecute Christians, and Atheists would persecute Deists, with as unrelenting Cruelty, as any Christians would persecute them or one another."

letter to Thomas Jefferson, 25 June 1813


"We have now, it seems a National Bible Society, to propagate King James's Bible, through all Nations. Would it not be better, to apply these pious Subscriptions, to purify Christendom from the Corruptions of Christianity; than to propagate those Corruptions in europe Asia, Africa and America!"

letter to Thomas Jefferson, 4 November 1816

He was not big on dogma or on bible-quotes, and the Ten Commandments on Government space would horrify him.