"It marks a betrayal of Washington's Kurdish allies, a betrayal that many other countries in the region will note with alarm," and " a stab in the back ." No, it is neither a betrayal nor a stab in the back. It has been a consistent U.S. geo-strategic policy for decades. The Kurds were used before and they are used now. It is not about Trump; despite differences, Turkey is a NATO ally.
“The West won the world not by the superiority of its ideas or values or religion (to which few members of other civilizations were converted) but rather by its superiority in applying organized violence. Westerners often forget this fact; non-Westerners never do.” —Samuel P. Huntington, The Clash of Civilisation and the Remaking of the World Order, 1996, p. 51