America doesn't go around toppling every bad regime in the world because--surprise!--we cannot. However, no one is allowed to admit that there are limits to the power of the great and might United States. So...we occasionally kick the shit out of someone with whom we have a beef anyway, AND that we are pretty sure we can defeat, eventually (Afghanistan, Iraq, Libya). And we let some of the other guys slide if they sell us oil (Saudi Arabia), play ball on Israel (Egypt) and/or let us park our ships and planes there while we kick the shit out of their neighbors (Bahrain). And we leave alone the countries where we might actually have some meaningful challenges in a conventional war, and where the local populace would likely hate us more than they hate their own government were we to invade (Iran--any wonder that they want nukes so badly?)
I'm disappointed that Obama has decided to join the Big Swinging Dick Club, but I can't say that I'm surprised.