The bottom line is that families were split apart and have remained apart for 60 years directly because of squabbling between the US and the former Soviet Union.
Directly because? Certainly the USA and the Soviet Union encouraged the hostility but the Korean people aren't robots. The reason North and South Korea are apart and have such lousy relations is because of Koreans. Non Europeans are also responsible for their actions.
Come on man. The USA and USSR literally drew the DMZ line at the end of World War II. Koreans didn't have much to do with that. Instead of reintegrating Korea into 1 republic, the two countries set up their own preferred style of government in each part of Korea. Nobody can argue that for the first few years after World War II, that the governments were anything but a puppet government. The US set up a South Korean constitution modeled after the US constitution, and the USSR set up communisim in the North with a hand-selected autocrat as the leader.
Korea and Vietnam were cold war fights by proxy. Maybe they would have had a conflict without foreign powers interfering, but the resources that the USSR and USA poured into the fight ensured that it was a far bigger, nastier, and longer war than it would have been otherwise. If either of the superpowers had stayed out of it, one or the other side would have won the war reasonably quickly. Both countries were responsible in creating the stalemate and both are responsible for the poor decisions of the past.
Its also important to keep in mind that outsiders of all types have been fiddling around in Korea since the 1600s- first the Chinese, then an incident with the American-owned ship "General Sherman", then the Japanese, then the USSR and USA. The History of Korea is not a very uplifting read. Korea has been shit upon by every country in their neighborhood and most of the superpowers as well. Given that history, it shouldn't be surprising that they turned inward and cut ties with the West and South Korea, which is strongly aligned with the USA.