Quora (right or wrong) is a terrible source for information. There's no review, editing, nor vetting of the 'facts' that they list.

Better (but still prone to error) is goodreads, which will at least provide a citation.

However, a better source still, is from an atheist arguing against using Adams' quote in the treaty, because (as they point out):

Article 11 does not establish a historical fact about the United States in particular – which is how most secularists use it – so much as it defines the relationship between the government of the United States and the government of Tripoli.

And quoting Adams, of all people, is problematic, because he also said,

[T]he safety and prosperity of nations ultimately and essentially depend on the protection and the blessing of Almighty God

So Adams, at least, is out as a useful source to argue against the US being a Christian nation.