Your description sounds very much like an old Poul Anderson story: "No Truce With Kings." First published in The Magazine of Fantasy and Science Fiction (June, 1963), it won a Hugo Award in 1964, and I believe I first read it in a collection of Hugo-winning short fiction edited by Isaac Asimov. It's set along the West Coast in some sort of post-apocalyptic future, after the USA (and other powerful nation states) have all fallen apart. Some of the surviving communities have embraced feudalism as a way to run things locally without being "loyal" to some huge, abstract governing entity. Instead, you are personally acquainted with the guy who calls the shots in your home town.
There is indeed a sort of civil war taking place in the story, and it turns out that the side that is pushing harder for a very strong central government is being supported by a powerful group called the Espers, who claim that their most gifted members ("the adepts") can communicate telepathically, exercise telekinesis as a weapon, and do other incredible things.
As you recalled, aliens eventually come into it. It turns out (as discovered by the main hero of the story during the war) that the apparent "psychic powers" of the Espers actually are faked with the help of super-advanced technology provided by a small group of aliens who, as you said, have been secretly trying to manipulate events "for your own good" based on their elaborate mathematical calculations of the way things ought to be to make Planet Earth a better place. Neither the aliens nor any of the humans were truly telepathic, however.
As you said, there was a certain libertarian feel to it. In one key speech near the end, one of the "good guys" makes an angry speech to the aliens about how silly they are to have assumed that reestablishing a great big government would automatically be the best possible thing for humanity. (I think he points out that every time in human history that someone has built a mighty empire to control a good chunk of the known world, other human beings have eventually torn it down again, and maybe this means the whole idea of empire-building is fatally flawed where our species is concerned.)
Here's a link to a page that lists all the times that story has been reprinted in one book or another.