Its to be remembered here that whiteness is as constructed as all other racial identities. For bigots like Trump its all about skin colour and white is "not coloured", a purely negative category with no attributes of its own. Thus why you can be a German Scottish American without hassle and you can be from one of hundreds of non-white cultures but its all just "black".
PS there are no biological races. Race is a matter of culture and the likes of Trump are all about cultural dominance.