I can't imagine mistaking a Japanese person for a Mexican. However, on a vacation in northern Minnesota, my first, thoughtless reaction on seeing Ojibwe Indians everywhere was "why are there so many Mexicans in northern Minnesota?" Since most Mexicans have more American Indian than European blood, I guess it's an easy mistake to make.
Part of the reason was this guy was a little bit pudgy, not part of the Japanese stereotype, And the pudginess of his face kind of effected his eyes. Never fooled me but I could see how someone not paying close attention might make the mistake.
A friend in Columbia Missouri I always thought was of Japanese ancestry told me his mother was from Alaska (as in native Indian)
I can’t imagine mistaking a Japanese person for a Mexican
I know a handsome young college student with a Latino last name and with a blonde Caucasian mom, and I assumed his looks descended from his Hispanic dad. Well one day I was talking with him, and it turns out that the guy I thought was his bio dad was his step dad and he adopted him, hence the Latino name. His bio dad was Japanese! He did not look at all Japanese. Interesting. He had darker skin than mom, and curly brown hair and almond eyes like his mexican adoptive dad!