Obviously we don't learn about unions at all. But the one that strikes me the most is the omission of the Battle of Blair Mountain, where the US government sent the army after the coal miners. https://en.wikipedia.org/wiki/Battle_of_Blair_Mountain
The Wilmington 1989 coup: After the Civil War, Wilmington North Carolina had a mostly black government. That didn't sit right with the whites, so they staged and successfully completed a Coup & overthrew the government. Only officially successful Coup to occur in the USA. https://www.pbs.org/wgbh/americanexperience/features/when-white-supremacists-overthrew-government/
9/11 - The much lesser known 9/11 occurs in Chili in on 9/11/1973. During a US sponsored coup, the revolutionaries smash an airplane into the capitol building. My not-so-conspiracy theory is there's a reason the US event happened on 9/11 as well. https://en.wikipedia.org/wiki/1973_Chilean_coup_d%27%C3%A9tat