The problem is that most of our Fantasy isn't written by Americans about American culture and values.Even American Fantasy writers write like they're British.Apart from his capitalization of the genre--English major pet peeve--I fail to see the problem with this situation. Yes, my favorite writers/producers are British--Lewis, Tolkien, Moffat, Neil Gaiman (though he currently lives in Wisconsin) and Jasper Fforde--but is there a problem with that? It's not like their characters go around eating scones and singing "God Save the Queen" every ten pages, even when the events primarily take place in "our" world. As for American values--er, I don't think we're doing so hot in that area either. Look at our economy, look at our crime rate, look at how causal we are about truth--modern (secular) American values are nothing to celebrate. And so many of the values celebrated by the best speculative works--self-sacrifice, friendship, strong leadership--should be INTERNATIONAL values, not merely British or American.
As for "even American fantasy writers write like Brits," my response is partially "so what?" and partially "you don't understand the genre. He mentions George R.R. Martin as a famous American fantasy writer, but dassifies him as primarily British for using a medieval-European setting. Seriously? America doesn't have hundreds of years of history to draw from--the oldest we can reliably refer to is the 1600s, which isn't old enough to have a mythic atmosphere, and records from further back are scarce, not to mention possible accusations of plagiarism from native peoples.
For "American fantasy," the article mentions two examples: Twilight and the Hunger Games. At least he acknowledges the poor quality of the former--but I'm still not sure the Hunger Games has the world-building of other famous series. Yes, it would be nice to have some American fantasy writers, but can we just keep looking for GOOD fantasy in the meantime?