Apparently, the US government did license export of anthrax samples to the University of Basra back in the eighties Anthrax strains are routinely transferred around the world between legitimate research labs. We did not supply them with weaponized anthrax.
Research labs in the US could order anthrax over the internet, at least until a few weeks ago. It's entirely possible, and even probable, that Iraq's anthrax came from US sources.
I don't think there's any evidence that we supplied Iraq with an anthrax weapon.