That is quite interesting, really. Though I fully admit that, without the help of the USA, western democracy would probably have been lost somewhere between 1930 and 1970, the history of the USA is not exactly brilliant. Where they have chosen to intervene in a situation themselves, they have usually made a pig's ear of things (eg Vietnam). What they have been really good at is sitting on the fence, taking economic advantage of other's troubles, and then jumping in on the likely winning side (eg WW1/WW2). In peace time, the USA utilises its relatively self-sufficient position to bully markets to its way of thinking. And, of course, it is in the interests of the States to have an "enemy" that maintains a threat that has to be guarded against.
The trouble is, history has happened and we are where we are - somewhat insignificant pawns of a crumbling hegemony