The Founding Fathers of the US Constitution were liberals. They were "Deists" who had trouble with the "Trinitarian" views of religion and the rigidity of the doctrine of Calvin. This is why they wrote that "Congress shall make no law with respect to the establishment of religion." They were afraid of the Religious Theocrats that existed in their time as well and saw them as inimical to the incipient Nation. They knew what the Puritans were like.
Thomas Jefferson was quite "liberal" with his interpretation of the Bible in which he excised much of the violence and left only the quotes he could live with. He passed his Bible version on to his friends.
In short, the Founding Fathers were Liberals in their politics and religion.
They believed in a natural form of a Supreme Being. It is referred to once in the Constitution of the US as a Creator. Otherwise, Jesus and God are not mentiioned once for good reason. No Trinity for them. They like all true Liberals cherished "diversity" in worship, something that was not found in the history of religion in Europe at that time.
Many of them such as Franklyn appeased the religous by acknowledging the "civilizing" effect of such beliefs but in private may have held either different views or not thought it important to think about much at all.
They would have been horrified to hear the noise that Fallwell and his ilk make that "the United States is a Christian nation". It is not and never was and hopefully never will become.