Comparing salaries without understanding cost of living and expenses does not give you anything useful.
In the US, you also have a very wide range of salaries depending on the where you live. The salaries in California and New York is much higher than in places like Texas, but the cost of living is much lower in Texas and there is no state income tax in Texas unlike California and New York.
In Japan, there are some expenses most Japanese do not have such as owning a car - because of the incredible public transportation system, you can live your entire life in Japan and never own a car and many people do not even know how to drive. In the US, everyone who owns a car pays about $8,600/year for maintenance, fuel, tax, and other fees not to mention toll charges on tollways. The average Japanese pays around $1,100/year for public transportation.
Furthermore, while the Japanese annual income is about $27,323 that is NET not gross. A salary in Japan also includes some sort of retirement pay they receive upon retirement.