And some demented mis-elected old man making a phone call will make a difference in all that?
Yes. If Israel’s enemies knew the United States stood with Israel, and would provide intelligence and logistical help (no troops) then it might cause those enemies to hesitate. As it now stands, no pushback will be expected from the US even if Israel’s enemies target civilians. Also, these countries and terrorist groups assume that if things don’t go well for them, the US and other “concerned” countries will run to the UN to sanction Israel and force it to stop. So, yes, it does make a difference.