Certainly the US has the best film, music, theatre, literature, painting, and arguably dance and opera as well.
MW - I don't think this is 'certain' at all. What US museum compares to the Louvre? Do you really that the significant trash that Hollywood produces enobles the world? Has the US produced a Shakespeare, a Dante, A Homer ( and I am not refering to Homer Simpson ). Certainly the Met can take first place on any stage, but where are our von Karajans, our Sir Neville Marriners? As wonderful as ABT and NYC Ballet are performing, I wouldn't say the are significantly better than POB, the Kirov, or the Royal Ballet. And finally, as much as I may enjoy Snoop-Doggy-Dog during the occasional run, he really isn't a Mozart ( or a Beethoven, Brahms, Berlioz, Bach, ... ) is he?
I believe that one measure of a civilization's greatness can be based on the art it has produced, and let's face it, in the broad sweep of time the US is still second tier. If we are not careful, the US's greatest 'artisic' legacy to the world will be that of creative consumption, and when it comes to creative ways to destroy the planet, if you can consider this a capitalistic art form, then we take second to no one.