Rolling Stone isn't going to run an article about the impact of Flappy Bird on culture in Tazmania or Greece; while it would be tangentially interesting, the subject's incredibly small proximity to the life of the average reader of the American version of Rolling Stone means it won't have the same impact.
Not a "just how Americans think" issue, a "what is relevant to our readers' lives" issue.
Aren't you are proving the parent's point there? You say that only articles depicting their own culture are seem as relevant to the american reader, which is what he claims.
That's absolutely not the case in other places of the world. In some cases, even the opposite problem arises (that is, discriminating against your own country/culture and favouring a foreign one)
No, I said an article about a culture only tangentially related to the reader will be less relevant than an article directly related to the reader.
(To note, the article wasn't about American culture, it was a personal interest piece on a person who was unprepared for the effects of the success he experienced.)
If by "other places in the world" you mean areas that are small enough or have an ephemeral-enough regional identity to have developed strong codependent identities with other regions, then I would certainly agree.
Living in a number of places has shown me that, in larger countries/communities with defined identities, internally facing publications will publish stories that are strongly relevant to their reader.
Because, as I said, it wouldn't make a lot of sense to spend that sort of space on an article that wasn't relevant to the reader.
As a transplant to America I agree with the difference in cultures but to be fair, you're comparing "other places of the world," which tend to be much smaller and more homogenous that the US, to a country founded as a loose federation of states divided largely along political and religious lines.
Cultural diversity (and exceptionalism, etc) is all rolled into the DNA of the country.
Not a "just how Americans think" issue, a "what is relevant to our readers' lives" issue.