No, it shouldn't, but Americans simply cannot think outside their tiny box. Title-holder should be India, probably -- among other things, the decimal number system we call 'Arabic' is actually Indian -- but then there's China, if you accept the Chinese definition of 'interesting', meaning 'cultured but spectacularly terrible', as in the supposed Chinese curse, 'May you live in interesting times.' Or I suppose there's Russia -- all those writers and composers (not so much painters or sculptors for some reason), but then again that staggering roll-call of tyrants and mass murderers. England doesn't quite count, because although its language is spoken everywhere and its law and culture and literature are spread far and wide, and there's no one like Shakespeare, the country's own insular history -- Boudicca, the Wars of the Roses, Cromwell, Pitt the Younger, the Industrial Revolution, the Reform Acts and so on -- are of limited interest to foreigners, who, being foreigners, have parochial preoccupations of their own.
This is so insanely subjective a question, even moreso because what we think of as the modern nation-state is very different from what it used to be, and what on earth counts as 'interesting' or 'vibrant' will be very different for everyone. Where history and anthropology have a legitimate claim to be seen as a science, this sort of particularly unscientific question is only really interesting for revealing the underlying tastes of the subject.