Bobert, yes, we used a WMD at the end of WWII. Since then, I believe that the US record is fairly clean.
Do you have documentation of any time in the last 50 years that the US has used nuclear, biological or chemical agents on either an enemy or it's own troops or people with malice aforethought.
I put that last in to forestall a diatribe about Agent Orange. When it was used in Viet Nam, it's devastating side effects were not yet known.

troll