There is absolutely nothing about private enterprise that enabled deficit spending or confidence in US’s future. The War Department collaborated very closely to retool existing industries and also help create entirely new ones by sharing technology and designs with the private contractors; it could have simply nationalized them and there would literally be 0 change in confidence in US treasury bonds. Fundamentally, the distinction on how you choose to organize your means of production doesn’t really matter all that much, and certainly doesn’t matter as much as you seem to believe.