Actually, Obama is such a big thing as he's potentially the first black US president, isn't it?
Just like electing Cain is a non issue, as he's white (read: European). What about the first Native Indian president, I am sure it'd be a big thing too.

All those aforementioned are Americans by nationality, but we human beings nonetheless associate people with their ethnicity. We can't help ourselves. Not necessarily negatively, but at certain level it is inherent to our brain.

And Asian is not a country, it's not a nation, this is not a discussion of nationality or citizenship, but ethnicity.