If I draw a stick figure, most Americans will assume that it is a white man. Because to them that is the Default Human Being. For them to think it is a woman I have to add a dress or long hair; for Asian, I have to add slanted eyes; for black, I add kinky hair or brown skin. Etc.
The Other has to be marked. If there are no stereotyped markings of otherness, then white is assumed.
Americans apply this thinking to Japanese drawings. But to the Japanese the Default Human Being is Japanese! So they feel no need to make their characters “look Asian”. They just have to make them look like people and everyone in Japan will assume they are Japanese – no matter how improbable their physical appearance.