I don't buy the explanation that this is all about US cynicism, opportunism and self interested inconsistency. Whatever you think of the action in Iraq, one has to recognise that American foreign policy is more often (not always, just more often) motivated by genuine altruism, fighting for freedom and democracy and 'doing the right thing' than any other nation's.
So there must be a cogent, moral explanation for the US failure to condemn Georgia's original aggression, and for the strength of support that we're seeing.