From what I can tell, we currently have plausible deniability from involvement, which we should keep. If we give Israel bunker busters, then we have certainly painted a target (bigger than now) on every US base in the Middle East. We have also removed any credibility as honest brokers in any negotiations with Iran.
Netanyahu has been wanting to go after Iran for decades. He has said they are "this close" to nuclear bombs for the same time period. He has wanted to drag the US into a war with Iran, just like he did everything he could to drag us into the war with Iraq, including Congressional testimony about how awesome the ME would be post-Saddam.
- Both Gabbard, in March, and the IAEA stated that Iran is not developing nuclear weapons. There were concerns from the IAEA about some access.
- Iran has had the technical ability to build nukes for decades. That genie is well out of the bottle. It hasn't done so. You can't bomb that knowledge away. Killing 9 nuclear scientists has zero impact either, they have hundreds in their nuclear program.
- Destroying their existing facilities may set them back a couple of years at best, what then?
- Assuming no regime change, the likeliest reaction from Iran would be that they need nukes, maybe just buy them from Pakistan or get the uranium there.