Paul Krugman explains (though perhaps a bit too defnitively for my tastes):
[T]he war in Georgia [marks] the end of the Pax Americana — the era in which the United States more or less maintained a monopoly on the use of military force. And that raises some real questions about the future of globalization.
Some have asked, “Didn’t the American-created global order suffer a greater defeat with the invasion of Iraq?” or “How is the Russian support of South Ossetian independence different from the US support of Kosovar independence?”
The US invasion of Iraq does have consequences for the stability of the international system. It does make it harder for the US to assert the importance of respecting national sovereignty. But, it did not alter the fundamental fact that the US economy, society, and culture tend to see their interests aligned with politically and economically free societies ruled by law. No one is surprised that, following the increasing democratic stability in Iraq, the US is getting ready to leave. No one is surprised that the US is helping to support a free society in Kosovo. Russia cannot be expected to act similarly.