How does impact if the US has the moral high ground? If anything, the reason South Korea isn’t entirely a communist dictatorship is because of the US soldiers who died there defending it (amount a number of other western countries).
The view is that Korea could be one united country and the war entirely avoided if the US had not capitulated to the Soviet demands. US soldiers did die defending South Korea from the North Korean and Chinese invasion, and that is admirable, but don't forget that far more Koreans have died and continue to die.
https://en.wikipedia.org/wiki/General_Order_No._1
The Soviets had declared war on Japan 9 days prior and were allowed control of half of Korea.