This is because in spite of its meek
professions of neutrality, Washington did take a side in this conflict:
that of Iraq's central government. But it did more than that by
attempting to minimize the role its regional adversary, Iran, apparently
played in the reconquest of Kirkuk. The commander of the Quds Force,
the foreign expeditionary arm of Iran's Revolutionary Guards Corps, was reportedly instrumental in the Kirkuk operation.
Nothing
better illustrates the incoherence of America's stance in the Middle
East than the fact that it turned out to be on the same side as Major
General Qasem Soleimani, who occupies a status within US intelligence
circles somewhere between Professor Moriarty and Darth Vader. He and his proxies are believed by US officials to have caused hundreds of American fatalities and injuries on the battlefields of Iraq.
Yet
it's hard to overstate what the Iranian operative has just pulled off.
Not only did Soleimani out-marshal and humiliate Washington by brokering
a cleverer and more cynical deal, which undercut its own vain attempts
at conflict resolution, but he was then rewarded with US legitimization
of his scheme. (Iran officially denied any involvement in the recapture of Kirkuk.)
-- Michael Weiss, "How America sided with Iran over Iraq's Kurds" (CNN).