Sure, but like I said, cultural boundaries have become more fluid today. We see many young white people adopting aspects of Black culture. Even Black people adopted aspects of Europeon culture as a means of excersizing power (one of the rules of a hegemonic society is that in order to excersize power you must adopt the cultural practices, i.e laws, norms etc of the ruling class). (I actually don't eat with a knife and fork btw ahaha).
I actually eat with chopsticks a lot haha
I'll address some of these points more further down.
Sure, there were minor difference, but if you contrast Christian norms and beliefs as a whole and contrast that with any other independent culture (like the hindu tradtions, african traditions etc) there are huge and stark differences.
Yes, that is true - but in actuality it was the Christian tradition that was held in common across ethnic groups, including in particular African Americans, whose traditions were often a little distinct but were more similar to the Baptism of the whites than to Catholicism.
Yeah I agree it was normative totally. But I do think that is a defining feature of white (European culture). I think we take for granted how much of the normative practices we have today that have their roots in European culture. It is why academics refer to the world as the Western world, c.f Eastern world, Middle Eastern world. Western culture, is pretty much European culture that has become pretty normalized in countries. Post Colonialism is a whole theory which deals with the ramifications of when two cultures (the European colonizers and the natives of a country) clash and how it leads to oppression, conflict and finally forging of a distinct culture.
I totally agree that Western cultures are essentially an outgrowth of the cultures of Europe, and in particular Western Europe and those areas influenced by Enlightenment values. We have no argument there.
What I would say is that an aspect of white privilege is that the culture which the white elites grow up with (this is all except for variant groups, essentially) is just the normative culture, rather than being one culture alongside others (in which case you'd have white culture alongside black culture). Any person has to conform to the social and cultural norms of the dominant group so as to more easily make their way in society. So Barack Obama, for example, is neither derived from, nor appears to particularly exhibit, the culture of the African-Americans. Culturally, he belongs to no particular minority culture and so can be said to be a member of American normative culture. But that doesn't make him a member of white culture exactly, because that implies switching between options, rather than acquiescing to the implicit demands for assimilation by the European-derived 'default' culture.
Obviously the situation is more complex than this - I grew up in an area of the UK where there were essentially two British cultural streams and ethnic groups, one in particular rather ill-defined.