True, the history books are generally written by/for the victors. Well, also written by people who make a living selling books to people who are willing to buy them.
Which is why we end up with textbooks that gloss over the fact that the civil war really was caused by white people who honestly thought they were so superior to black people that it was even okay to own them, like cattle. (Side-track: I have heard it argued that most white southerners didn't even OWN slaves. True, but that didn't stop them from believing IN slavery and my best guess is the lack of ownership had more to do with not being able to afford a slave.)
Of course, after public school, you should be getting exposure to somewhat more diverse sources of information. Eventually, you come to realize there is more to history than what you were spoon-fed as a child.... Or, apparently, not.
The shared article is worth reading. If the things you read in it come as a surprise, you should consider reading some history books that were not authorized by a public school board.
Be warned, you are in for some other shocks as well....
President Lincoln wasn't actually interested in freeing the slaves. He was about trying to strengthen the union. By the time he issued the emancipation proclamation, the Confederate states were already in revolt.
The founding Fathers were not all Christians. Some of them were, yes. And some of them were deists, pantheists, even at least one known Unitarian (and if you think Unitarian = Christian, try asking any Baptist or Catholic what they think of a Christian that doesn't believe Jesus = God [look up trinitarianism then look up Unitarianism].
Thanksgiving .... Ask pretty much any Native American what they think of thanksgiving and you're likely to get an earful, if they're willing to talk to you about it at all.
Speaking of American Natives, just about anything you were taught about the settlers and the pioneers and their dealings with the "Indians" was crap.
And why did the Europeans call them Indians when India is such a long way away? Because Columbus thought he had found his new route to India (Cathay, China Japan, the Indies). And you probably already knew that but did your history class spend any time on the genocide of the Tianos?
I have to make myself stop or you'll never get to move on to the article.
You're just lucky I am writing this on a tablet. If I had a real keyboard, I probably would have written a lot more and with citation links.