To entirely defeat and destroy Iran’s nuclear program with CONVENTIONAL forces alone, I think the US woud have to do it. If Israel attacks, it would either have to use nukes, or be satisfied with just doing severe damage to the program, but without a real knock-out punch. And of course, Iran would also launch SOME sort of counter-attack.
I’ve also heard there is some question if Israels bombs can reach their sites, as they are so deep underground, even if use of latest bunker buster.
Therefor, if she does strick and does not take them out, certain nations are considering taking out Israel’s planes ,that carries these bombs, in order to devert Irans retaliation and possible all out nuclear war.