There is also a major distinction between the ability to inflict damage and casualties, and actually occupying a territory with its nation. In post WW2 history I don't know of any such territory or nation that has been successfully controlled by the US, while China did nearly double its territory. Yes, it was relatively peaceful and weak Tibet, but still. No other powers even dared to think about intervening in this unjust occupation.
In general it's hard to say which nation is more powerful. Often, dollar figures are used to express the might. But then there is a reality check. The supposedly militarily most powerful country has a big time problem controlling a country with an economy 5.5 times smaller than the economy of New York City. Looking at the reality, at how much money was wasted in Iraq, and how bleak the outcome has been so far, one might think that Iraq is #1 military power, sharing the honor with the US. After all, there is a stalemate at best
