It is definitely US centric. It is also very Apple-centric. Many times I see a blurb "New app X that does Y" which sounds interesting only to click on it and because they use url shortener/redirect find out it is either a direct link to the ios store or that it is an ios app. It would be nice if they would indicate that something was only for one platform or at least directly link to the page so you could see that it was a link to apple or google or whatever before clicking on it.
It makes sense when a community starts with a group of people from smaller community and later on expands to other areas and communities. It has been what, 6 months since PH's launch? Its a great MVP refactored out of Show HNs!
it is definitely a great product. what I like about Show HN is that it utilises reputation systems but lets everyone submit creating less of a filter bubble experience. Anyway, as you said, its only 6 months old. i just get the feeling though that people living in the valley can't actually see or understand the filter bubble I'm talking about.