There are many reasons history has been so demoted in schools ... and homes! Many children don't see their grandparents on any regular basis nor have any idea about earlier generations. History doesn't begin as a subject in school, but as stories told by parents, grandparents, and older adults, to children, the good and the bad, the happy and the sad. Then a child is ready to think about even earlier generations in the classroom.
If kids don't have this connection, history is just blather. Also, it is not in the tests used to test students and fund schools, so there's not much incentive for teachers to emphasize it. Now, it has become politicized, so almost any facet of history is going to engender rage in some population of parents on one subject or another.
One of my early historical sources was being allowed to read, during free time, at my own choice, Uncle Tom's Cabin. Yes, this was written by a middle-aged white woman with a specific point of view as an abolitionist, but at least it raised the subject and the period in my mind and gave me a foothold on the subject without having to contend with parents, administrators, enraged activists on one side or the other, and so on.
U.S. history was one of my minors in undergraduate school, and I had some stellar courses, among them urban history taught by Arthur Osophsky at what is now University of Illinois at Chicago (not to be confused with University of Chicago), and U.S. Intellectual History taught by a visiting prof from George Washington U. in St. Louis, in summer school at University of Missouri at Columbia, when I had been admitted to grad school there in journalism, just as the Selective Service people caught up with me. That was the end of my academic career until I went back to grad school on G.I. Bill in a different field.
Kids don't know which came first, the French and Indian War or the Revolutionary War, the Korean War or the Persian Gulf war, and so on. As for Ancient History, European History, 5000 years of Chinese History, and so on, this is all darkness in young adults' memory banks.