I think that's a slight exaggeration, although I get what you're saying. But I think it's important to demonstrate to libs that I'm being consistent so I'll explain what I mean.

I don't think the communal decision making bodies that spun up in the wake of the Japanese evacuation were necessarily completely aligned with Kim or the communists in exile, it was virtually impossible to maintain a functioning domestic apparatus and what I've read makes it seem like these were mostly improvisational.

That said, I think in the long run you're right, I see it as similar to Vietnam later: because US foreign policy was aligned with elements that were naturally unpopular to the population of the country (in Korea's case, the Japanese and domestic collaborators) a democratic resolution of the question of what sort of government a united Korea would chose for itself was not going to be an acceptable outcome to the US.

But we don't know what they would organically choose for themselves because that decision was foreclosed by US occupation. I suspect a popular referendum was the best possible outcome but I think it would probably look very different from the current DPRK, for understandable reasons.

The US created south korea out of thin air at the end of WWII, literally just drawing a line on a map.

Then they both held elections. The south's election was rigged by the US, who used their sway at the UN (the USSR was boycotting at the time and PRC still hadn't been accepted) to get South Korea's puppet state recognized as the gov't of all Korea, including the parts that didn't even have the US's sham elections. As preparation to invade the north, the US purged any non-compliant elements from the gov't (going so far as to put compradors who'd worked for Japan during occupation in high ranking positions) and carried out massacres of elements likely to side with communists (such as rural villages that lead communal lifestyles).

The north saw America was coming for them and the longer they waited, the worse position they'd be in.

Well you're a dumbass if you can't understand this lol. What the fuck does the American Civil War have to do with this? Nobody forced the slavers to make a separate country. Meanwhile the US forced the south of Korea to set up a government and refuse any discussion with the rest of Korea. You can define invasion however you want but it's nonsense to define how you're trying other "governments tm" being how you define it