The destruction of the Japanese navy almost completely destroyed their home islands. Cities were destroyed, industrial capacity gutted, and stockpiles exhausted. Government officials stood without respect or prestige
A journal excerpt from a person involved in the event in question
The most notable is the atomic bomb. Roosevelt became aware that the Nazis were trying to develop one, so he started the "Manhattan Project" which was a group of elite scientists tasked with developing their own atomic bomb. They eventually succeeded, and in 1945, we dropped the bomb on Japan.
The US supported South Korea which has a democratic government similar to the US while the Soviet Union supported North Korea, which has a communist government similar to the one the USSR had.