All right, I agree I forgot Philly, which has as well a well known museum that you didn't mention, (Philadelphia Museum of Art which is home to Van Gogh's Sunflowers and Cezanne's Large Bathers, Picasso, Maigritte, Duchamp, Chirico, Miro, Mondrian, Pollock, Kandinsky's works of art-I travelled to PA just for its visit), so let's say, that DC (mostly due to its National Gallery), Philadelphia, New York (Moma, Metrop., Frick Collection) and Chicago (Chicago's Symphony) is all that one of the biggest and most developed world-wide countries has to offer? (Culturally speaking) Let's add that the rapid growing cities in the south (which are prone to become the largest by the statistics specially if the mexican immigration continues at this pace) have no cultural offer whatsoever. Even if you take any tiny european village (let's say Santiago de Compostela, Carcassone, Lucca) the difference is such that you can't speak on equal terms of european and american cities. USA stands for consumption, malls, and dvds.
If we speak of attractions, that's a different point, but I don't think that Ghirardelli Square, or Pier "21"-was it?- stand for "culture"? Or for the same token, the sequoias or the well known and boring (to death) Alcatraz prison tour....very very pretty but that's not what I was speaking about. When it comes then to attractions, I could post 1001 argentine attractions but I believe and I guess that you already know that was not my point. Now, the question goes...is SF a great cultural pole because of an acceptable opera house? I wouldn't say so. Or for the case LA due to a tycoon's private collection? (Paul Getty's Museum). A city of 9,935,475 souls(2005 estimate) with one "well known" private museum......... I wouldn't say (and I suppose you agree) that touring Rodeo Street or Beverly Hills can be called "culture"
Good Night and Good Luck!