If the US sanctioned Israel, the very next day the Gaza massacre woull stop and Bibi would out, and within a week probably in jail, not only because Israel's oldest ally turning against them like that would be the stronguest possible message that they fucked-up, but also but because losing support from the US would be seen as an existential threat for Israel.

The talkie-talkie from the US Administration that's as far as the US goes at the moment (accompanied by the very oppsite of the words in actions such as military and diplomatic support) is rightly seen as hot air produced merelly for Biden's political convenience.