Almost anything related to Abraham Lincoln. I will preface this by saying that no, I'm not a butthurt lost causer, and yes, the South was largely fighting to keep slavery legal. This isn't about the Civil War, but about how Lincoln is portrayed today vs who he actually was.
Lincoln is used as a tool to teach modern 21st century values, and his role is quasi-religious. Slavery is treated like America's original sin, and Lincoln died to free us from that sin. There's a narrative that Lincoln spent his life opposing slavery on humanitarian grounds and that he was in favor of racial equality. That narrative is largely fictional.
The real Lincoln was a corporate railroad lawyer before entering politics. He openly said his primary motive in the Civil War was keeping the Union together, (this quote is commonly repeated by lost causers to claim the Civil War wasn't about slavery), and in the same quote said that he didn't particularly care about slavery beyond how it would affect American unity. He also considered whites to be superior and blacks to be inferiors, believed that equality wasn't possible, and integration was undesireable, and because of this wanted to send the freed slaves back to Africa. In line with this, his oposition to slavery (less staunch than often claimed) was less motiviated by humaitarianism and more motivated by a desire to protect the economic interests of ‘Free White Labour’. If you want to get a bit politispergy, he had one of the largest paramilitary organizations in America’s history(The Wide Awakes), who jailed journalists for reporting negative things.
THAT Lincoln, the man who made Trump look like a respecter of his critics, the man would be considered horrifically racist by today's standards, is so far away from the "Great Emancipator" Lincoln presented in the modern narrative, its absurd. The whitewashing of Lincoln is imo one of the best examples of revisionism in American history.
Like I said, I'm not a lost causer and the Confederacy had plenty of grounds for crticism, to put it mildly. That doesn't justify Lincoln being deified and protrayed in popular consciousness as a figure that he never was in reality.
A sort of revisionist stance that's gotten really common is associating Confederate ideology with fascism (and also distancing it, which bland normie conservatives do too, from American republicanism and liberalism in general) just because it's racist, as if that were a necessary characteristic of fascism (it's not) or equivalent to it.
In reality, the closest equivalent to the Southern worldview was something like Roman republicanism (the existence of slavery makes liberty more meaningful, and slavery is necessary to sustain a leisure class capable of politicking; the Southern planter, who tended to dabble in law or medicine or military service, was more like the Roman aristocrat than anything else). The Union, on the other hand, had similarities to fascism with its strong Yankee nationalism, protectionism, corporatist (state subsidizes the industry, works with the banks) economy. There's a reason nationalists and fascists the world over admired Lincoln. It wasn't fascist, but if a person is going to slap retarded labels on things then it's the Union that fits it better, the Confederacy was its own bizarre and unique thing.
I've heard people talk about Southern ideology like they didn't understand liberalism, no they didn't misunderstand it you condescending twat, they had a completely different version of it.
SOME OTHERS
Again, not actual revisionism, but more like revisionism-by-omission: Jonestown gets a lot of play either as a Christian cult or as a generic cult, and in popular memory it's very rarely remembered as having been a Communist movement that fused with the San Francisco machine. I feel like it's sometimes used to make points about muh religion when it was in reality very little to do with Christianity or the Bible by the time it took off.
Popular memory also whitewashed the hippies completely, they had a very aggressive, violent, criminal tinge to them. Their peaceful nature was a pose, not reality.
The way Leftists have become associated with the party of science is baffling and probably driven mostly by dumbass creationists, because pretty much every fucking technology (especially agricultural) except green they've been opposed to, and they did nothing but bitch about the Space Race.
There seems to be this big shift to give Blacks credit for absolutely everything in music (like with everything else in this world), and also to cast it like some antagonistic thing that White musicians "stole" their music. Usually it's just jokes, implying there'd be some resentment about people like Elvis Presley, but I find it very disrespectful because those people got their music from hanging out with Blacks at a time when that was not approved of. It also dramatically understates the importance of the White instruments, music theory, and genres that enabled it and the huge Jewish role (you could probably argue jazz is as much Yiddish as it is Black).
Schrodinger's Racist, a phenomenon in which all the racism in the US exists in the South except for when it's politically important to remember that discrimination was widespread in the North too. (The North is not racist and the South is, except the country is entirely racist everywhere: the contradiction.) I rant about this frequently.
This obnoxious trend where people portray the Fifties black-and-white TV style family as socially dysfunctional and repressed MORE than the modern American family, it's like this form of projection where the modern man says "well if I can't see your degeneracy you must just be hiding it and even more degenerate than me."