The key point to bear in mind is that Russia cannot be in Europe without Ukraine also being in Europe… — Zbigniew Brzezinski

Moreover, as America becomes an increasingly multi-cultural society, it may find it more difficult to fashion a consensus on foreign policy issues, except in the circumstance of a truly massive and widely perceived direct external threat.

With the more endowed nations constrained by their own higher technological capacity for self-destruction as well as by self interest, war may have become a luxury that only the poor peoples of this world can afford.

To put it very simply, anyone can become an American, but only a Chinese can be Chinese - and that places an additional and significant barrier in the way of any essentially national global hegemony.