The US has to be very careful about how they go about doing that. If they end their military protection of Israel, or even appear to be considering it, that could risk Iran and others wanting to try to exploit the situation, and cause more instability and more conflict. The next logical step is to put politicians with genocide rethoric on the sanctions list. It's not going to be enough, or satisfy anyone, but it would be an historic step to take and line up a path towards putting Nettanyahu himself on a future sanctions list.
They have to do it step by step though, they can't be seen as abandoning or going against Israel.