Japan can be seen as a victory for the US in the Cold War because it ended up firmly in the Western camp.
The victory in Japan began at the end of World War II. As the war was ending, the US prevented the Soviet Union from occupying part of Japan and gaining a foothold for communism. After the war, the US pulled Japan farther into its orbit. It created a new and more democratic constitution for Japan. It also helped to make Japan an economic power. By making Japan more democratic and more prosperous the US cemented Japan as stronghold of capitalism and democracy in East Asia.