Power and corruption goes hand in hand. US being a superpower is a rough test of the democratic process as well as the democratically elected leaders.
Any other country would have faced similar problems. On thing though, US is a rather fundamentalistic nation these days and the fanatic approach on the "American model is the best", has started to create problems around the world. The strong militaristic tradition that today is the basis for US nationalism and patriotism, might in the near future create unbearable situations for US as a super power when it stretches itself to thin around the world.