Your link Jom basically backs up what I have stated

US renounced the use of chemical and biological weapons sometime around 1966/1968 about ten years after the UK had done exactly the same thing.

US still remains the main world-wide centre for the storage of chemical and biological agents for destruction, the activity that the facilities mentioned are employed in. The agents from all over the world are not under the control of the US military, they are under the control of an independent international body responsible for supervising and verifying that those stocks of chemical and biological agents are destroyed - the sort of thing that the UN insisted that Saddam Hussein had to do.

Last time US forces specifically trained in the use of chemical weapons was deployed was during the Korean War - you get that from your wiki link Jom.