My guess is that the US will not attack Iran, either directly or via Israeli mercenary pilots flying US aircraft (which would be called an Israeli attack).
We do know that in the past year the US has provided over 100 advanced jet bombers to Israel, which already had a larger and more advanced air force than any NATO power (apart from the US itself), very openly advertised as capable of attacking Iran, and equipped with “special weapons” (whatever that means; it’s not explained). The goal may be to provoke Iran into some action that can provide a pretext for attack, or — more likely in my opinion — as an effort to provoke the leadership into harsher internal repression, which will incite resistance, and help break up the country from within, a long-term project. But we don’t know — and I doubt that US planners know.
I also don’t think that the US/Israeli military-intelligence can make an informed guess about what the response would be, from Iran or the world generally. The historical record of such predictions is awful. And there’s little point speculating about it. Rather, as usual, trying to do something about it. We’re not passive observers, or at least need not be.