When people speak of "Western culture," it's a euphemism for white culture. There's no difference, the two terms interchangeable in discussions of cultural superiority by the likes of Richard Spencer and other white supremacists.
Depends on what we're talking about when mentioning "Western culture," I suppose. Most of the what the west exports, culturally, is derived from contributions by African Americans. Fashion, music and dance are all heavily informed by black Americans. It's why the term "culture vulture" has become so popular, because there isn't a country where adoption of the African American cultural aesthetic isn't occurring.
But that's not the "Western culture" white supremacists like Trump are referencing. What they mean is "white society," where white people are dominant, controlling all of the wealth and power. That's the "Western culture" they're speaking of, the "browning" of which they wish to guard against.
