Keller argues that no one "worked for nothin' in that war," insisting that if he has to go to jail, then "half the Goddam country" is similarly culpable.

No, Keller is in constant denial about his role in the faulty parts. He tries to justify himself with arguments like the one you mentioned. Inside, he knows he is culpable if not directly responsible for the death of those pilots. We can see Keller's guilt eat at him until he kills himself at the end of the play.