That is not valid logic. The USA ratified the Chemical Weapons Convention in 1997, and there are various Acts of Congress which make most work on nerve gas a federal felony. There are no such legal prohibitions on AI development.
2. Nerve gas is not strategic. A better comparison are nukes in WW2.
3. Nerve gas has no other uses unlike AI.
4. Nerve can only be used to hurt unlike AI
5. If AI in military is so dangerous, should the US just sit and do nothing while China /Russia deploy it fully? What is your suggestion here specifically?