Once upon a time there was the rise of the Soviet Union and Japan. One doesn't exist anymore and one had it's bubble burst back in the early nineties from which it never properly recovered. China (and to a lesser extend India) are both rising powers but both still lag quite far behind the US in many ways. For one just take a look at the UN Human Development Index. They are way below many countries and have enormous internal issues of which the US has nothing like. Of course in recent times the US has been badly hurt by the financial crisis, it's military is badly stretched and true enough it has some internal issues of it's own but it will recover like it has before. Financially weaker perhaps but militarily it will remain dominant. For a while now we have had three major economic blocs. The European, The East Asian and The North American so the US is used to having other economically powerful nations and blocs. That's the future, not individual countries. China and the US both depend on each other. This is unprecedented in imperial history. So the likelihood of war between the two are slim.
