An oath to an oath? WTF?
You're asking for my help or my blessing or just as a witness. That's not an oath to me. An oath is a promise for you to do something. You asking (invoking) me for something.
So if you think that this was an oath to God this whole time, how could we ever expect to uphold it? And why was any airmen ever discharged for failing to follow their oath? After all, it was to God and not to us the citizens of the US according to you. He should be the one deciding, shouldn't he?
It's considered an "extra" penalty for making such an oath. Don't be strawmanning here. Just because I am making an oath to follow a duty, such as protecting the people of the US, while making that oath to god, doesn't mean that the only reprisal should come from God.
Don't be fucking asinine here. The point of such an oath to the deity is that even if you break the oath and don't get "punished" for it by some of those you are making the oath by, then the last reprisal will come from the paranormal entity you ascribe to.
Think of the oath people take on the stand for a court proceeding. The basics is as follows.
"I swear to tell the truth, the whole truth, and nothing but the truth so help me <insert my favorite paranormal entity here>"
Think about why that last part is there? It's to instill into the person making the oath that if they lie and aren't caught the hope is that the paranormal entity they ascribe to will "catch" them eventually and mete out appropriate reprisal. Thus the oath is not just to the court proceeding and those there to, but also to that paranormal entity.