If Iran won a war against Israel at least some of the more extreme in Iran want extermination. You could potentially be trading an incredibly one-sided war with a possible second Holocaust. Many of the most extreme political factions in surrounding countries want Israel wiped off the map and replaced with a Muslim theocracy. If you destabilize the area you’re risking worse than is currently happening.

I don’t think that means the USA should be giving Israel a blank check, but I’m also not a foreign policy expert and I suspect the diplomatic situation is far more complex than you and I can comprehend sitting comfortably on our couch. Especially since holding Israel accountable is also not as popular domestically as it seems in online communities like this one. So any diplomatic pressure has to be behind closed doors.