I had no idea when I was younger how much of school history is just introducing shared mythology and indoctrination. History is so much more interesting to just read about instead of the mythology selected by state education boards.
The one that comes to mind is the discussions of the two World Wars. When I left high school, I basically believe that both of them were basically good vs evil stories, where Europe was sucking at stuff and then America showed up and defeated the bad guys. My history classes basically ignore WWI only to say that a bunch of people died in trenches and then America showed up. WWII, the British and French were losing, and then America showed up. What's an Eastern front? Normandy. America is awesome. The end.
The first time I started actually learning about World War I and started realizing that the Germans were pretty much as innocent as anybody else in that conflict (and probably more innocent than, say, the Russians or the Austro-Hungarians, or the Ottomans), I was like "wait, what?"
Also, that the US didn't really do much from a combat perspective (though financing the whole thing for the Allied Powers certainly helped).
Some Myths I Learned in School that Reading History and Anthropology Corrected
1) The founders cast off autocratic tyranny and invented power checks, individual rights and the rule of law.
While monarchs in Russia, France and Spain frequently cited tradition, religion and even pagan mysticism to certify their absolute rule, things were a bit different in England. Republican government and rights of the ruled were part of the English system for a long time before 1776. They were mostly hard won by nobels (mostly for nobels) but none the less, proto constitutional law like Magna Carta, Parliament and the Civil Service preceded the founding by many years. American government may have been born of revolution but it was just an evolution of ideas and practices that had been developing for centuries.
2) America, and particularly Lincoln fought the Civil War in a nobel effort to end slavery.
While obviously the Civil War was triggered by the inability to resolve the issue of slavery the motivations of the primary participants aren't clear. From Robert E. Lee's initial opposition to secession to Lincoln's writing, "If I could save the Union without freeing any slave I would do it, and if I could save it by freeing all the slaves I would do it; and if I could save it by freeing some and leaving others alone I would also do that." it's clear that the war wasn't about "what was right" but what the individual actors wanted. What's really stunning about the narrative told in schools is just how close the government came to not abolishing slavery. The 13th amendment actually failed to pass the house once and that was with no Southern states holding seats at the time.
3) The Americas were largely empty when Europeans discovered them.
They weren't.
4) Neolithic people and hunter gatherers largely lived in peace with the planet and each other. For lack of a better term, they lived as "nobel savages".
To the contrary, the lives of these people are characterized by frequent skirmishes between bands, blood feuds and ritual killings. "Nobel savages" living all over the globe managed to drive extinct more than 50% of large mammal species well before recorded history. They also shaped the earth and warped plant life far from anything you could rightfully consider "natural".
I could go on about Martin Luther, the "Fall" of Rome and the Russian Revolution but I gotta get back to work.