The real United States died 160 years ago, when it decided that being a member of the Union was no longer voluntary. It was replaced by an evil empire pretending called "The United States" that went on to terrorize the rest of the world, and continues to do so to this day, all for money.
This isn't a defense of the Confederacy; the secession was absolutely about slavery and it was evil, but that doesn't mean that the Union were the good guys for fighting them. The Union became an evil empire.
The Southern economy was built on slavery, and straight up taking away slaves would kill it, unless they were compensated and could transition their economy. The South went to war to keep their slaves - their wealth - because Lincoln wasn't willing to buy out the slaves like the British government did with their slaves.
The North didn't go to war to free the slaves. The North went to war for... you guessed it: money. You don't see a lot of Union propaganda telling people to die to free black slaves. The propaganda was about "preserve the union!" (read: "Preserve the empire!). The Northern elite wanted to maintain the money coming in from the Southern ports, which were 75% of the ports in the US. If the South seceded, the US government, which was funded by tariffs, would have to find some other way to do it.
Once the North finished their conquest of the South (don't forget the mass rape of Southern women, but history is written by the victors and they mostly certainly don't teach that in history class), the new American Empire proceeded to ravage the rest of the world, using whatever they can to "justify" their new conquest. See the conquest of Cuba. Or the conquest of the Philipines. Or the conquest of Japan. Or the conquest of Korea. Or the conquest of Hawaii. And so on. When a vassal state becomes too powerful to comfortably control - like Japan - the US then treats them as an enemy and levels them into the ground and enslaves them once more. (NOT defending the Imperial Junta; yes those people were batshit crazy, but that doesn't make the US's response right)
Make no mistake: Lincoln and Roosevelt aren't heroes. They were evil emperors. And the American generals who indiscriminately bombed British and French and German and Chinese and Japanese cities are no heroes either.
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RE: Revolutionary War talk going on above
I've seen that historians like to downplay the efforts of the local American town militias, focusing on the Continental Army. Yes, statistically the milita were terrible in traditional battles, but big battles isn't what won the war. It was their efforts outside of the big battles that won the wars. They were the insurgency in cities stealing and destroying British supplies. They were the information net that saved Washington's ass time and time again. They were the ambushers who killed the most British troops. Most combat in the Revolution wasn't in big battles between armies, but ambushes and small skirmishes by the militia. And for the big battles between armies, the militia were essentially for acting as "speed bumps" to slow down and deter the enemy's advance while the Continental Army got set up. They were the true heroes.