Richard Adams has really interesting item on Obama invocation of John Adams in his Cairo speech. Here’s the beginning:

In his Address in Cairo President Obama said: “In signing the Treaty of Tripoli in 1796, our second President John Adams wrote: “The United States has in itself no character of enmity against the laws, religion or tranquility of Muslims.”
As a close student of the founding era, I was surprised to find that I did not recall Adams saying that. That Adams was not President until 1797 tipped me off that something was askew. Some research turned up this phrase from Article 11 of the Treaty of Tripoli which President Washington negotiated and which was ratified by the Senate and signed by President Adams in 1797:
As the government of the United States of America is not in any sense founded on the Christian Religion,-as it has in itself no character of enmity against the laws, religion or tranquility of Musselmen,-and as the said States never have entered into any war or act of hostility against any Mehomitan nation, it is declared by the parties that no pretext arising from religious opinions shall ever produce an interruption of the harmony existing between the two countries. I suppose saying that Adams “wrote” that (with some silent elipses) is close enough to the truth for a politician.
But there’s more to the story. That passage, apparently was absent from the Arabic original (and therefore presumably official version) of the treaty, translated by Joel Barlow…