I don't think you know what a nation is. The Korean people are a nation - from the Latin root natus, they all share a common birth. However, there are two states, North Korea and South Korea. Both of them are internationally recognized states, meaning we currently have one nation (Korea) split between two states. The split between these states is entirely a construction of imperialism. The people in DPRK and the people in the occupied South do not constitute different nations nor is the 38th parallel a historical division within and among the Korean people that would constitute a meaningful boundary for their self-determination.

The Americans had no business being there at all nor demanding a partition of a nation of people. They did so as part of maintaining colonial occupation for the purpose of anti-conmunism both against the USSR and also against the emerging PLA in China. The US destroyed everything north of the 38th parallel to punish the portion of the Koreans who decided they would not allow their country to continue to be a colony. The USA bombed the countryside until pilots literally went on bombing runs and came back with full payloads because there were no more targets left to bomb. The USA used so much napalm that Koreans needed to live in caves.

The southern portion of the country (land) that was inhabited by the nation of Korea (people) was turned into a new state (South Korea) by the USA and purged of all people who would oppose them and their ideology. South Korea is ONLY separate because of an international legal fiction perpetrated by the US against the Korean people (the nation of Korea).

The leadership culture of the South was built entirely on subjugation to the US war machine. Leaders survived or failed or died based on their allegiance to the US military occupation. The transition from full occupation to what exists today is one of loosening the leash on a captive one inch at a time to confirm that the punishing dominance has had the desired effect - that effect being complete subjugation to the interests of the dominator.

You think the Korean people want US nukes on submarines in its waters? You think the Korean people want to have half of their homeland completely inaccessible to them? You think the Korean people want half of their people to be completely isolated from them? You think they like having the DMZ as an eternal reminder of the constant threat of readied lethal force directed at their own countrypersons?

One day, there will be one nation-state of Korea, and the division created by the imperialists will dissolve and the trauma of this period can begin to be integrated and healed by the Korean people, but it will not happen until the US loses its violent dominance over the Pacific region.