The problem is there's no doubt that most Americans at the time were Christian (excluding Amerindians), and of course slaves were forcefully converted. Jews and Islamists were also present in America then.

However, the majority being Christian did not make America Christian in it's origin under our Founding Fathers who were of the Enlightenment philosophy. The bulk of the Christians were largely so by birth, and it was often only observed only on holidays or rare special occassions like baptism, christening, marriage and funerals.

Methodists and Baptists weren't even around yet, at least not in America. The earliest mention of Baptists were in 1534, and it was toward a vaguely identifiable group in England that opposed infant baptism. Methodism didn't form until 1738 when the Anglican priest John Wesley developed it, but he remained to his death an Anglican priest.

The first Baptist Church in America was founded by Roger Williams in
1638 in Rhode Island, and during the founding of our Country didn't extend far from there until the second great revival period of 1790's to 1840's, but because they were Congregational in nature, never were a powerhouse in government. That's why the Baptists were among the first to claim seperation of Church and State to protect themselves from larger denominations like Episcopelians (Anglicans) and Presbyterians (Church of Scotland), as well as Roman Catholicism.