Why don’t North Koreans have as much freedom as South Koreans?

Japan had nearly full control of Korea around 1910. When the Japanese empire dismantled, the country split. America helps and somewhat controls South Korea. Since America doesn’t force people to have strange beliefs, South Koreans have freedom. However, the North Korean government forces beliefs that seem strange onto its people.
Most of these beliefs are either about how “great” their leader is, or how “evil” America is. Some of the things that people are taught in North Korea are that their leader is pretty much a god and is the best at everything. They are told that he invented the hamburger and doesn’t need to poop. People are also made to believe that the rest of the world