I've been reading for quite a while now. Your improbable scenario was that Israel was telling us to fall into line or they would use their nukes. (They did that once you know. It's called the Samson option). By the time things came to that pass it's quite possible that Israel would not be an ally and some of those other countries might be. I could see us use our nukes to take out the silos. But the scenario is a bit silly so the speculation is too.
I think it is important to realize that it is not ordained by God that the US will protect Israel. That relationship is showing much wear and tear. We might be told to fall into line once too often by that pipsqueak piece of desert.
Israel does not tell us to "fall in line". Israel, like every sovereign nation, has a right to self defense. As a part of that self-defense, she has equipped herself with nuclear weapons.
Israel does not blackmail us with those nukes. The simple fact is that everyone know that the destruction of Israel will likely mean a nuclear strike on the richest deposits of oil on earth. Contaminated oil is not in the USA's interest. So it's not blackmail that empowers this relationship, it is mutual self interest. The Arab states are the aggressors, have been for 50 years. The USA knows that Israel is afraid of being overrun, and knows that if she is overrun it will be bad for us. So, we protect her with a little money and some diplomacy to keep that oil flowing.
Note that Egypt gets 2/3rd of what Israel gets, which only goes to prove that the purpose of our relationship is stability and nothing else. All sides have enough power to destroy each other, which we hope is just enough to prevent either side from actually trying.