since world war 1? first, you cannot discount america's defense of france and england toward the end of ww1. that is significant - england was long the home of moderate republicanism and the alliance of france and england and america was the ONLY power defending constitutional republicanism in that war. it was a decisive victory of democracy over autocracy and monarchism. in the second world war, american arms were essential in defending freedom from both fascism and communism. and the following four decades were a long string of defenses against totalitarian governance in favor of free and civil democratic society.
today america is still - you cannot discount this - it is still the defender of the european union and japan/south korea/australia. were it not for america, russia would easily dominate all of europe, given europe's largely non-existant defense force, as well as that of japan/south korea. china would dominate the east and russia the west were it not for the united states. you simply cannot discount the enormous amount of effort, blood and treasure america has expended in defense of a substantial portion of the world that exists in free society.
yes, america has had to pick and choose. that is because it is still only a minority of the world that exists in the free realm. but that realm has grown to the point of at least 1/6 of the globe and put at least another 1/3 on the trajectory toward freedom because of america's balanced picking and choosing. after all there is only so much 5% of the world can do. but it has done a lot. perhaps it is partially self interested, but there is also another part that is selfless. you could not have asked for a more benevolent, even benificent, global power.
america's "insane" military budget is not just for america. it is for england and italy, france and germany, the nordic and low countries, now for central and eastern europe, for turkey, egypt and israel, for india and japan and new zealand and australia and south korea. it is also for substantial parts of south america. it is for canada and mexico. it is a large sphere of free and civil societies - you cannot discount this and see that the burden was only limited and that the effect was only self-interest. yes, there was self-interest, but self-interest in doing what is right is still doing what is right. people under the US system are simply put, better off. there is really no serious contention to that claim. and the extent to which they are better off, compared with the early monarchical systems defeated in WW1, or the fascist systems defeated in WW2, or the communist systems defeated in the cold war, and the "islamist" systems that we fight today - there is no comparison between the superior american-lead system of free society, civil liberty, political democracy and economic advancement, and the backward and oppressive regimes america has fought.
i will concede that today it has become fashionable to reject america and to say its value are backward. believe me, we have been fighting the same arrogant mindset at home, because we were the first to realize just how backward and ignorant and spiteful the right in the united states can be. but ultimately, my country is an unparalleled force for human freedom and it deserves to be defended and loved - even loved despite the criticism - and it is important to understand the difference between short-term missed political opportunies as represented by bush, and the long term defense of human freedom that the entirety of america's history represents.