I think it helps to illustrate the Enlightenment theism that wasn't strict deism or orthodox Christianity that captured the mind of certain notable Founders. Though they may not have agreed with every jot and tittle of Priestley's theology, Jefferson, J. Adams and Franklin, among others, were greatly influenced by it. Interestingly, Priestley's "rational Christianity" -- where brilliant minds like his could use their reason and brilliance to discover novel "rational" understandings of the Bible -- failed to accurately prophesize the events of their age.
Priestley believed the Book of Revelation foretold the triumphant success of the French Revolution. As John Adams explained the story:
Not long after the dénouement of the tragedy of Louis XVI., when I was Vice-President, my friend, the Doctor, came to breakfast with me alone. He was very sociable, very learned and eloquent on the subject of the French Revolution. It was opening a new era in the world, and presenting a near view of the millennium. I listened, I heard with great attention, and perfect sang froid; at last I asked the Doctor, “Do you really believe the French will establish a free, democratic government in France?” He answered, “I do firmly believe it.” “Will you give me leave to ask you upon what grounds you entertain this opinion? Is it from any thing you ever read in history? Is there any instance of a Roman Catholic monarchy of five-and-twenty millions of people, at once converted into intelligent, free, and rational people?” “No. I know of no instance like it.” “Is there any thing in your knowledge of human nature, derived from books or experience, that any empire, ancient or modern, consisting of such multitudes of ignorant people, ever were, or ever can be, suddenly converted into materials capable of conducting a free government, especially a democratic republic?” “No. I know of nothing of the kind.” “Well, then, Sir, what is the ground of your opinion?” The answer was, “My opinion is founded altogether upon revelation and the prophecies. I take it that the ten horns of the great beast in Revelations mean the ten crowned heads of Europe, and that the execution of the king of France is the falling off of the first of those horns; and the nine monarchies of Europe will fall, one after another, in the same way.”