Danbury Baptists that a wall separating church and state would prevent the majority Congregationalists in Connecticut from denying Baptists the rights of citizenship, he couldn't have predicted that non-establishment of religion by the government would enable the establishment of so many religions.
If America were truly founded as a "Christian nation," there would have to be a definition of "Christian." And if there were an official religion, and it was "Christianity" by whatever definition Congress would have chosen (it would have been Anglican), then none of these beliefs could have developed:
1812 Reformed Mennonite Church
1816 African Methodist Episcopal Church
1863 Seventh Day Adventist Church
1875 Christian Science
1881 Church of God (Anderson, IN)
1886 Church of God (Cleveland, TN)
1908 Church of the Nazarene
1914 Assemblies of God
1916 Jewish Science
1917 Jehovah's Witnesses
1920 Reconstructionist Judaism
1927 International Church of the Foursquare Gospel
1953 Church of Scientology
1955 Branch Davidians
1957 United Church of Christ
1968 Disciples of Christ
1973 Jews for Jesus
Non-denominationalism is all the rage since then:
Prosperity theology, televangelism, and megachurches from the 1980s to today represent the trend toward non-denominational churches. Though technically non-dogmatic, most of these seem remarkably similar to Southern Baptists in their beliefs. By distancing themselves from any central authority, they can tailor their dogma to the wishes of the pastor(s) or congregation.
After all, if any denomination is free to practice in the U.S., then a denomination of one congregation is free as well.
Dominion theology, in which Christians seek to have dominion over everyone else in their "kingdom," has also gained some traction. Coincidentally, it really took off after Roe v. Wade established abortion as a woman's right.
Religious freedom has been a two-edged sword. Believers are free to sell their souls to whichever belief system wins them over in the marketplace of ideas. But.... they have to let the heathens, hypocrites and heretics have their way, too.
I wonder how many American Baptists know they owe a debt to concept of a "Wall of Separation" between church and state.