Oh, where to begin? First, I do NOT believe that, due to the 14th Amendment, which you can look up. It prohibits the states from violating the Constitution in their own constitutions and laws. It was ratified in 1868, far earlier than your 1947 bugaboo you so love to scapegoat. Prior to that time, any states wishing to join the union had to conform to the Constitution as a condition of entry. See Article IV, section 2. Because of communication, and of plain resistance, some states took their time (decades in some cases), but all eventually conformed.
It seems we have both read the Constitution. The difference is, I see what IS there, and you see what you WISH was there. As for Thomas Jefferson's quote, it quite nicely puts another nail in America as a "Christian Nation", as he quite clearly speaks AGAINST an establishment. His reference to the states was trumped by the 14th Amendment.
You are into the realm of spinning.
Some 24 years after the 14th Amendment was ratified, in the "Church of the Holy Trinity vs. United States" of 1892, the Supreme Court ruled unanimously that, "this is a religious people. This is a Christian nation", adding, "Our laws and our institutions must necessarily be based upon and embody the teachings of the redeemer of mankind. It is impossible for it to be otherwise; in this sense and to the extent our civilization and our institutions are emphatically Christian."
Who should I believe? You and the ACLU low-lifes, or the 1892 Supreme Court? BTW, you misread the Jefferson quote. If you were not so predisposed to believe the ACLU you might see it correctly.