Do Americans call Biracial a person who looks biracial only?

I consider most of the people above white because I don't know their racial composition.(If I find out I will consider them whatever they are) I don't think that people are being racist they just don't know. Many people are 1/2 another race but don't look like it and many do. It's all about appearance nothing scientific. When will people realize that race or how many races you are does not matter?