If you want to study the weakness of American foreign policy under the Obama-Clinton-Kerry Administration, just look at the Turkish-Kurdish-Syrian triangle.
America's formal position is that it opposes the Assad regime, that it looks on Turkey as a close ally, and that it arms the Kurds in their fight against ISIS.
ISIS is considered a potentially major threat within America and must be eliminated. The Kurds have been the bravest, boldest fighters against Islamic State. Yet, recently Vice President Biden, during a visit to Turkey, demanded that the Kurds return back over the river from Syria into Iraq. The Kurds were the first and only force that took on ISIS in Iraq on behalf of the slaughtered Yezidi people. They were the first to win significant victories and drove much of ISIS back into Syria where they pursued them.