http://money.cnn.com/2016/10/10/technology/thisis2016-michael-luo-nytimes/index.html
Judging from the incidents that Asian American was told to go back to China, China seems to be Asian representative country for white people.
On the other hand, Japanese cannot distinguish French from American.
So, most Japanese call Caucasian American. Then, United States seems to be treated as representative of Caucasian in Japan.
