They probably weren't "the" first; but they were our (that is America's) first.
This collection of "Political Sermons of the American Founding," Ellis Sandoz, ed. provides extremely informative material that illustrates the political-theological dimension of the American Founding.
The collection includes not just the most notable "Whig" sermons, but also some "Tory" loyalists.
I've long studies this dynamic and am known for seeming to endorse an understanding of "Christianity" that is anti-liberationist.
As it were, the "liberty" the Bible speaks of is entirely spiritual (freedom from sin or its consequences) not political at all. Jesus didn't overturn one social institution, not political tyranny, not divine right of kings, not chattel slavery.
And Christianity, properly understood, is entirely compatible chattel slavery and demands believers submit to government period, even if said government is a pagan tyranny as was Nero's, arguably the ruler Paul told believers to submit to in Romans 13.
Now I am not a "Christian." So it's really not up to me to personally endorse any version of the faith or say who gets to be a Christian. For my own personal reasons, anyone who calls himself a "Christian" gets to be one, even if he is a atheist. Jefferson thought himself a Christian and certainly passes my very easy to pass test for what is a "Christian."
But my own personal reasons are just that. There are competing definitions of what Christianity means. And some take their faith more seriously and define it more narrowly.
The Church itself, since at least 325 AD, has carefully guarded orthodoxy and put heretics in not a good place. There is interesting debate on whether heretics merit the label "Christian." I've uncovered quite a bit from orthodox believers who answer that question negatively. There's more to come.
Perhaps heretics merit the label "Christian" as an adjective, but not as a noun. Arians and Socinians, (or to use more current examples Mormons and Jehovah's Witnesses) as it were, are not "Christians," but believe in a "Christian-heresy."
But to bring us back to Sandoz's collection, historically up throughout the Protestant Reformation, the understanding of Christianity and liberation that I outlined above (I would argue) prevailed. That is, the "orthodox" guardians of the faith did not endorse the notions that the Bible teaches political liberty rights, a right to revolt against tyrants, any more than it teaches Arianism or Socinianism.
But if you look for *thought* that predates the Enlightenment that questioned the prevailing orthodoxy, you'll almost certainly find it. Indeed, "Christian" figures from the Enlightenment tended to embrace Arianism, something that goes back to 325 AD. Ditto with theological universalism (universal salvation, something in which a number of notable early church fathers believed).
It was after Henry the VIII, Luther and Calvin (all of whom, by the way, were with the Roman Catholic Church in endorsing the notion that men do not have God given rights to political and religious liberty, to revolt against tyrants, etc.) -- after much schismatism -- did authorities question their traditional understanding of the Bible and political liberty.
An interlocutor, trying to find official Catholic sources for the idea of resisting tyranny (I'm sure there is much "lower" Roman Catholic chatter, but we were trying to find top down authoritative sources), pointed me to POPE PIUS V'S BULL AGAINST ELIZABETH (1570).
Well, it doesn't say anything about believers having a God given right to resist tyranny, tyrants losing their Romans 13 status as "rulers," or "rulers" somehow having to pass a test of "godliness" or justice in order to qualify as "rulers." But it does speak of "usurpation."
And indeed, were there not a "usurpation" of power by Henry the VIII, the Church wouldn't have dealt with the circumstance in England POPE PIUS V'S BULL discusses.
But it was during that period -- after Henry the VIII, Luther and Calvin -- problems with persecution within Christendom (Catholic persecuting Protestants, vice-versa and Protestants persecuting each other) lead to more "liberation" talk. So much so that said talk became a "meme" within Christendom. And it was mainly those on the receiving end who did the loudest talking.
And Sandoz's collection features when the Christian liberation talk reached fever pitch.
The million $$ question, though, is: Is it sound theology? On a personal level, as a non-Christian, I really don't have an answer.
But I can make an analogy: I see the pro-liberty sermons in Sandoz's collection as classically liberal liberation theology. And that kind of liberation theology is about as authentically Christian and hermeneutically sound as modern collectivist liberation theology.
[The most notable anti-liberationist present day evangelical preacher is, of course, John MacArthur. You can hear him discuss the liberation theology of the emergent church here. The funny thing is every single criticism of MacArthur towards them could be raised against the Patriotic Preachers featured in Sandoz's collection.]