Re: Iraq, Afghanistan, coups, etc.
Iraq was a farce. We lacked cassus belli, and so manufactured one, aided by Saddam's intransigence. His crime was being belligerent in the face of a painfully hawkish, self-interested administration. Sure, he wasn't a good person, and indeed had committed crimes against his people-- but we've ignored far worse when we didn't have other interests.
Afghanistan-- well, there the Afghan government was harboring an organization that had just executed a major terrorist attack, and refusing to cooperate in turning them in. We supported an existing resistance movement in achieving the collapse of the established government. Not unlike Libya, I think that was well-executed. The issue, much like any prior Afghan entanglement (going back to the British mission in 18-whatever), is that the country is an exceptionally hostile environment for an occupation, and we shouldn't be in the occupation business anyway.
The Ukraine-- well, here's the thing. We certainly recognized the new government quickly, but this has all the hallmarks of a popular uprising after public opinion turned against the existing government. While international bodies naturally have an interest in the inviolability of governments and the maintenance of the status quo, one could argue that so long as an outside power didn't foment the uprising, then it has validity insofar as any popular action has validity. This is hair-splitting, of course? But a coup is de facto antidemocratic, where in this case it is a popular movement overturning prior democratic action.
So. Really, when you get down to it, the issue now isn't the validity of the interim Ukrainian government. The issue is that Russia perceives a threat to its interests (in the guise of 'violence against ethnic Russians,' which I've read no reports confirming), and so is using the unrest as grounds to seize territory.
Consider, if you will, that Latvia and Estonia also have large Russian-speaking populations. If at any point there's unrest there, will this justification be used for annexation of another state?