No guarantees will ever, ever, ever be enough when it comes to US and israel. The day they end the war, they will block any transactions to Iranian banks, put back sanctions on Iran and start threatening Iran once again. Then the cycle will repeat for the 4th time.
Remember, these are the same two countries who were negotiating with Iran for weeks, so that in the background, they can gather the movements of Khamenei to launch an attack. They can never be trusted with any promises and they will find their way around any guarantees.
The only guarantee Iran can get .. and which will show the sincerity of US, will be to ask US to vacate its bases .. ask for end to War in Lebanon and Gaza and ask for end to West bank settlements.
Unless US agrees for these, they won't be sincere in anything else either.