The Treaty of Tripoli was ratified unanimously by the US Senate in 1796 and signed by President John Adams. Article 11 of the treaty stated: “As the government of the United States of America is not in any sense founded on the Christian Religion...” As a ratified treaty that statement is US law under the US Constitution since 1796.
For additional and corrective context.
Will just note that there were those who sharply disagreed with that being in the treaty at the time; I would have been one of them. My opinion is that it was included to address Tripoli’s concern that a Christian nation would attack them solely on the fact that they were Muslims, and that the language went too far. Would also note that Tripoli broke the Treaty in 1801. (And yes, I do believe our nation was founded on Christian principles, and absolute conviction that our humanity arises from divine creation and not the laws of the state.)
My understanding is that the English version of the document, the one actually signed, never contained that language. An Arabic version did, which was the one shown to the Tripoli Muslims to quell their concern we should be considered “Christian”, therefore their natural enemy.
...something like that - but it was my understanding that this was never actually in the English, signed, version.
Clearly this country was founded by Christians and everything that flowed out of it is saturated in Christian doctrine. The very concept of “inalienable rights from God” does not derive from atheism and certainly isn’t compatible with Islamic doctrine. So, if such concepts aren’t Christian, what are they?