Well, he is right so it should not be in the Onion. He does not say the USA has not fought any major wars, just that it hasn't won any. If anything the name Department of War is far more honest about the purpose of the institution, namely fighting and - presumably - winning wars. The Fire department is called so because it is tasked with fighting fire, it is not called the Protection from Incendiary Hazards department for a reason.

Will this name change suddenly make the USA any more successful in winning wars? That is doubtful at best but I do prefer the lack of euphemism in this new old name. War is dirty business and the more this is made clear the better it is.