The founders knew and understood the true implication and impact of the separation of Church and State for the country compared to the religious tyranny that enveloped Europe at the time and before this country started developing into a nation essentially free of mandated spiritual influence, which some call Christianity.
The freedmen were not really free in 1865, nor are most of their descendants really free in 1965. Slavery was but one aspect of a race and color problem that is still far from solution here, or anywhere. In America, particularly, the grapes of wrath have not yet yielded their bitter vintage. — The Oxford History of the American People [1965], ch.1