Why block the Syrians from regaining control of their own oil field?
If China took over US oil assets would you have a problem with that?
Also - the Syrians spent their blood and treasure evicting ISIS - the force of murderous terrorists that Obama created, armed and sicced on them. Isn't it about time that America f*cked off out of the country?
If it found supporting ISIS to be politically useful, it would do so in a minute.
As for the oil field we do what we do because it's useful militarily and denies support to the Assad regime which has allied itself with our enemies Iran and Russia.
I find the notion that if we acted "on principle" and gave up the oil field then the Chinese would be persuaded to behave better highly dubious.