The question becomes, is culture as distinct as it was before? I'd argue it's not. If Lord of the Rings was so popular in the US, does that make it not part of US culture? Some cultures for example, Canada, UK, US share similar interests and lifestyles. Like Grakelin said, popular books get published everywhere. And this is often true of popular anything. Taiwanese kids singing Whitney Houston songs. The suit became a world standard for dress, is it somehow part of ___ culture (whoever first came up with it)? Is English only English culture because they came up with it, but Americans use it? If anything, it is the UK that won the 'culture war' in that their language and customs dominate the US, Canada and Australia, and in turn more of UK's specific culture has permeated the world than any other specific culture. Is the northeast of the US winning the culture war against the midwest or the south?
The real cultural differences come between a western country and say, Pakistan, or Egypt. Maine (where I'm from) is more similar to Canada than it is to Georgia. So are we Canadian culture? When I went to England they had KFC, when I went to Japan they had McDonald's, and when you come to the US we have a huge amount of European based culture. More and more, in a consumer based world, a product is judged not where it came from, but on its own merit and whether that population enjoys it.