Why does US need to remain in Syria?
Let the Turks, Iranians, Kurds, Syrians, Russians, the Wagner Group, and Saudis fight it out or fix it themselves. It's their neighborhood, and we are not their colonial nor imperian masters.
As long as US troops are in Syria, they will be targets for anti-American interests. Bring the boys home. They did their job - they prevailed over ISIL.
American troops cannot solve the conflicts of Sunni Islam vs Shi'ite Islam; Saudi Arabia vs Iran; Kurds vs Turkey, Syria, and Iraq; Iran vs Israel; America vs Russia's Syrian interests; Europe vs growing Indian and Chinese influence, etc.
We don't need their oil, anymore. Let's get the hell out of there.