The Federalist Papers were a big chunk of reading materials for my introductory US History course in college. I think it was briefly covered in highschool too (AP classes), but probably no more than an issue or two.
I recognize that still, only barely "most" Americans even go to college, so probably only like a third ever really read any of it.
Most people don't take college-level American history courses, even among those that do go to college.
My AP history course was just basic American history with added reading and writing and a big project due near the end, taught using a college textbook. They weren't covered in much more detail, and definitely were not a big chunk of reading materials. Our extra reading included things like Malcolm X, The Grapes of Wrath, and... I can't remember the third. I think I that AP test was my best-scoring, but it has been 20 years so I might be wrong on that.
I recognize that still, only barely "most" Americans even go to college, so probably only like a third ever really read any of it.