Where Are the Great American Rabbis?

At Slate, Shmuel Rosner wonders whether Jewish America haslost its chance to foster home-grown rabbinical sages :

The Jewish world of the 21st century has very few, if any, rabbis and scholars universally accepted as “great” or “sagely” who are admired even by those outside the specific sect, stream, or group on which the rabbi in question presides. Jewish communities around the world have been unable to find suitable successors to those “last ones.” The problem is particularly manifest within the American Jewish community.

This is a relatively new and perplexing phenomenon, and it’s difficult to pinpoint why great American rabbis seem to be a thing of the past. Within Jewish tradition, the thesis of the “decline of the generations” (in Hebrew: Yeridat Ha’Dorot) is a very prevalent one, inversely related to the distance from Sinai. Is what we see in America today proof of this thesis (though not all great Jewish thinkers accept it)? Is it a problem with today’s rabbis, students, and scholars? Are we in the early years of a drought in Jewish thought? Or maybe the problem is not the rabbis but rather the changing times and changing nature of Judaism, which makes it more difficult for anyone to acquire greatness.