Which is easier, American or Japanese?

The U.S navy was right. It's easier to become a Japanese citizen. Basically, as long as you have a formal job in Japan and have stayed for enough years (usually 5 years), you can be naturalized. Japan's population is now experiencing negative growth, and the policy has intensified its efforts to attract foreign talents.

However, it is difficult to obtain permanent residence in Japan (equivalent to American green card), which generally takes about 10 years.

The immigration policy of the United States has been very conservative since 9 1 1, and it is basically one of the most difficult countries in the world to obtain permission.