The US could have stuck around, but this is part of Trump's bring them home strategy, which has no thought for the consequences of doing so. There were only about 100 SF troops there, as I understood it, and now Kurds are dying and IS fighters are getting loose.
This has always been Erdogan's plan but he is another fascist, who has been playing at being Trump longer than Trump.
Of course, by causing an issue in the first place (see China, Mexico, N Korea, etc), Trump will then try to "resolve the issues" prior to the next election, thereby showing his diplomatic skills and then claiming he should have the Nobel Peace Prize.
Who cares about the Kurds anyway - they weren't on the beaches (ironically, from someone who managed to avoid going to Vietnam).
Trump 101