But it is somehow OK, since he writes it for the European audience who also doesn't live in America.
I guess it would be possible to build a system of perceived American values from abroad. Perhaps with so much information and so much exported American culture (via Hollywood movies for example), it would be possible to get a fairly accurate idea of what American values would be !?
But then again, an expert is an expert if there are enough people calling him that, so as long as there are others who share the same (possibly skewed) interpretation, the author will probably be considered now a local expert on Americanism.