I disagree. The US is not going to seal its own death warrant over Israel, regardless of what the neocons want. Nuclear deterrence is a game of chicken, as i've mentioned earlier. There is a reason no weapon has ever been used since more than one country had nuclear devices. The moment you break no-first-use, there is no reason to not unload your entire arsenal in a massive second strike. Why wait to get hit (possibly again)?

Keep in mind that the first use will activate _all_ nuclear powers that feel threatened. So while the Israeli first use would not activate the US/Brit/French arsenal, it would activate the remainder of the arsenals around the world. Not just Pakistan. I suspect there are a few secret nuclear states that did not see an advantage to revealing this.

Consider also, the destabilization of a first use. Once it happens, the use of the weapons will become commonplace. I don't see how this ends anywhere short of a full strategic exchange. This has been noted by smart people for a very long time now; seems like the idiots in charge aren't taking it seriously.

Israel is very aware that using a nuclear weapon means the end of their state and the killing of the vast majority of their population. If they were to do so, the entire world would curse their names forever. Which seems apropos... and possibly the ultimate fate of a state that should never have existed in the first place.

Edited to add: nuclear weapons are not wonder weapons. They cause a lot of damage, but they are just very big explosives with some interesting after-effects. People getting comfortable with this is what needs to be feared.