It was an accurate description of the America at the time; entirely Protestant with a smattering of Catholics.
And it frankly has nothing to do with separation of Church and State.
Separation of Church and State is the REASON this country is so religious, actually; no country in the world has had it for a longer time. The countries of Europe have had (and many still have) official state-supported churches.
>> Separation of Church and State is the REASON this country is so religious.
LOL. You are some idiot!
Separation of Church and State is a new-fangled invention of the atheistic left. Only a fool would believe it.
You're making the mistake of equating religious sect with universal moral principles founded on theism. Moral absolutes based on religion are essentially the same in every monotheist religion, what to speak of Judeo-Christianity.
The "separation of Church and State" is a ficitious statement. Jefferson wrote it, but in a letter years after the founding of the country, and to a group of Baptists (IIRC) who were considered a minority religion.
Universal moral absolutes founded on religion has NOTHING to do with an established state religion, which is what the writers and signers of the Constitution wanted to repudiate.