The answer is because you come from a majority white country, and due to the tropes of animation. Most of the time, anime characters are not drawn to look white; they are cartoons and cartoons are meant to be cyphers. Understanding the implied ethnicity of a cartoon character comes down to a conversation between the audience and the creator, just like all art. Cartoons, be they western or Japanese employ a visual language known to the creator. Visual languages are constructed through context, and the audience may miss an awful lot of the language if they do not share the creator’s context, leading to misunderstandings. This happens to all art. The audience brings their own context to the piece. If you have the same context as the creator, you are likely to understand them more easily. But we Westerners bring our own context when we watch foreign media, and vice versa. Animation is a global medium now, and animators influence each other from opposite ends of the globe.