I'd call it a team effort. The US was certainly selling dual use equipment in the war, and not only did it not lift a finger to stop the use of chemical weapons, it blocked the UN Security Council from even passing a resolution saying that using them was a bad thing.
America also provided rhetorical cover for Iraq by accusing Iran of using chemical weapons as well. Allegations which were never substantiated, probably because it never actually happened.
And when the Reagan administration learned that Iraq was targetting their own Kurdish population with chemical weapons, they still didn't give a shit. But two decades later, when Bush the Younger decided to emulate his father, the American government invoked those gas attacks against civilians as a justification to dismantle Iraq. Two decades late for the Kurds that got gassed by Iraq while the American government pretended not to notice. American foreign policy is depraved.
