I know the term is relatively recent, starting with Harding. Irrespective of that, as an immigrant it always struck me as odd how much the men who broke this country away from the British Empire seem to be treated as almost mythical figures. This seems particularly odd given the values of equality and "of the people" which are so foundational to the US.
Given the recency of the pledge of allegiance for example, I'm curious as to whether this quasi-sainthood is recent and, if so, what led to it. I'm also obviously open to being incorrect in my perception.
Not to discourage further discussion, of which I am sure there can be plenty, but u/DarthNetflix has answered this question previously here
In my search for that answer that I recalled, I also found this older response to a similar question if it interests you where there's some interesting answers though the responses aren't as academic, which is understandable as I am sure things on this sub were more lax 8 years ago.
Most nations around the world have mythical founders, who are credited with establishing the nation and in many cases providing it with its system of government or religion/cultural values. However most of these "founders" are often ancient and legendary folk figures. In this regard the US is no different, however being a rather young nation, it does appear odd why ordinary statesmen and lawyers who lived 250 years ago are so heavily idealized almost to the extent of having divine influence.
The saint-like treatment of the "founding fathers" is part of American exceptionalism, which has existed since the beginning. The US was one of the first federative republics in the world, and the American values of liberty, autonomy, limited government, made the US "exceptional" in the eyes of its people from day one. Great importance was placed on the US Constitution and the "framers" (i.e. founding fathers) behind it, who were portrayed as brilliant statesmen who wrote an exceptional document that was very liberal for its time because it restricted the powers of the state for the benefit of the "liberty" of its citizens which was apparently inconceivable to most of the world across the Atlantic.
Americans have always had a strong independent spirit, and their nation is based around shared values rooted in their Constitution. That is what unites a very diverse young country together, hence why American exceptionalism rhetoric is very common in US politics today and has increased since the US acquired superpower status post-WW2.
As for the religious aspect of the saint-like worship of the founders, this exceptionalism combines Christianity with civic nationalism. For example, during the Cold War (when the exceptionalism rhetoric was amplified) the biblical phase "City upon a Hill", from Jesus' Sermon on the Mount, was used by American politicians to describe the US; it was first used by JFK and then popularized with Reagan's famous "shining city on a hill" quote that explains that America acts as a 'beacon of hope' for the rest of the world that desires traditional American values such as democracy, liberty, equality, balance of power, limited government etc. Today this phrase is still used by US politicians. The religious dimension behind American exceptionalism has led to the saint-like worship/deification of the lawyers and statesmen who drafted the Constitution.
This is the reason why Americans are so hesitant to change/amend the Constitution (like regarding gun rights) even though it has been amended a grand total of 27 times since 1789, because they think it is a perfect document, every word is meant to be, and this explains the success of the US.
The US is a great country in many ways, and this explanation is just about why the "founding fathers" are revered as saint-like.
To add to the past comments written on this topic, you can generally point to the first generation after the founding, as the framers themselves either died or retired from public life. Obviously, this isn’t universal. Some faded from prominence and have never recovered or were held in lower regard until decades later.
The earliest popular example of “deification” was Parson Weems’ “The Life of Washington,” in 1800. Over multiple additions it added apocryphal stories including the chopping down of the cherry tree. Weems added a religious tone to his biography that would be carried forward.
Putting Weems and the deification of the framers into period context, the Second Great Awakening began around 1800. There’s a nascent form of Christian nationalism that becomes more visible in the ensuing decades where the Constitution and its authors are seen as guided by divine providence; especially the ones like Washington and Franklin, who are dead and unable to contradict the narrative.