Japan is 2.1 times larger than Oklahoma (USA).
Area: 377,915 km2 World Factbook
Population: 127,103,388 (July 2014) World Factbook
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south. Wikipedia
Oklahoma is a state located in the South Central United States. Oklahoma is the 20th most extensive and the 28th most populous of the 50 United States. The state's name is derived from the Choctaw words okla and humma, meaning "red people". Wikipedia