Too little imperialism?

I am not a fan of the US, I have no sympathy for the American way of life, for the fundamentalists, for the fast food chains, for Hollywood and the hypocritical talk about value-based politics. And for many other things. I wouldn't be happy to live in America. But looking at the mess the world is now I think that the Americans have missed a historic chance to put this world in order, to make it a better place. In my childhood the Soviet press was full of attacks against the "American imperialism". But perhaps the mistake America made was not to become really imperialist. It would have meant to issue in 1946 an ultimatum to the only real competitor, the USSR, and to make the whole world the US zone of influence. It would have meant that all other nations would have been in a situation similar to what Western European nations were in the times of the Cold War. But there would have been no cold war, no arms race, no big wars in Asia and Africa, probably also no mad dictators as Idi Amin or Pol Poth. Tamerlan is quoted to have said that the world is too small to tolerate many rulers. This is nowadays more true than ever. The tragedy is that it is no more possible to unite the world under one ruler, under one centre of power. The only chance to make the world a better and safer place would be something similar to the Vienna Congress in 1815 that established a consensus between European powers guaranteeing peace for nearly a century in the continent. Nowadays it would mean finding such a consensus between the main big players -- the US, China, Russia, Europe (although Europe still has not succeeded in finding a common denominator in its relations with the outside world), India and some emerging nations of Asia and America.