McGrath- perhaps our difference on the "empire" question is primarily semantic. I associate the word with forcible conquest and annexation, as for example the Alexandrian and Roman Empires of ancient times, or the British Empire of late, and perhaps also the Third Reich. I also tend to think in terms of Monarchies or Dictatorships when the word "empire" comes up.

If you view an Empire as a large nation-state with world balance-of-power overtones, I might agree that the US is one. Brazil might be stretching it. Personally, I think there should be a better term to describe Super States (and no, I don't like that one either) in the 21st Century that isn't quite so redolent of colonialism and conquest.