Remember though that if not for US action, there would be no South Korea; there would just be a larger and more terrible North Korea, and millions more people would live in suffering and bondage.
Personally, I don't think the US should have intervened in Korea, for all the very good reasons that your founders cautioned against foreign intervention and entanglements.
But the intervention saved millions from enslavement. It was a net benefit to everyone in South Korea, then and now.
It wasn't the US alone - it was a UN-mission under the lead of the US, more than twice the South Korean soldiers fought than US soldiers, and don't forget all the other coalition forces who also fought: the British soldiers, the Turkish, the Australians etc.
If we go back even further, Korea as a whole was under Japanese rule. If the US negotiated with Japan instead of going all out, Korea wouldn't have to be split apart to begin with.
Also, if there was no South Korea, then who knows, maybe the "larger" North Korea would just be like China today; kind of terrible but not so terrible.
Without the US-backed South Korea, China would not be so interested in backing [North] Korea, and indeed would see them as a realistic threat rather than a client/buffer state.
Personally, I don't think the US should have intervened in Korea, for all the very good reasons that your founders cautioned against foreign intervention and entanglements.
But the intervention saved millions from enslavement. It was a net benefit to everyone in South Korea, then and now.