Not only did Sean Spicer say that Hitler never used chemical weapons, but Secretary of Defense Mattis said:
Even in World War II chemical weapons were not used on battlefields. Even in World War II, chemical weapons were not used on battlefields. Even in the Korean War, they were not used on battlefields.
Since World War I there’s been an international convention on this.
But U.S. used chemical weapons against civilians in Iraq in 2004. Evidence here, here, here, here, here, here. The use of those weapons greatly increased the rate of birth defects.
The U.S. armed and supported Iraq after it invaded Iran and engaged in a long, bloody war which included the use of chemical weapons. The U.S. provided chemical weapons to Saddam Hussein to use against Iran.
Here is former Secretary of Defense Donald Rumsfeld meeting with Saddam in the 1980’s, several months after Saddam had used chemical weapons in a massacre: