But that's what Adams wrote in a private letter in 1816, well after he'd retired from the public stage. What he said on the public stage was this, in his 1797 inaugural address:
"I feel it to be my duty to add, if a veneration for the religion of a people who profess and call themselves Christians, and a fixed resolution to consider a decent respect for Christianity among the best recommendations for the public service, can enable me in any degree to comply with your wishes, it shall be my strenuous endeavor that this sagacious injunction of the two Houses shall not be without effect."
One blogger ran with Jon's post to claim the "most bloody religion" quote as proof that the United States was not a Christian nation. Mr. Rowe rightly replies that that's far too much to read into that quote. As for this quote, I'd say it's also too much to read into it to say that Adams did believe it was a Christian nation.
But I will say he certainly sounds like he's addressing one.