One is a country, one is an individual, to say that any individual is more important to the war than the United States is the literal definition of Great Man Theory (i.e. childish nonsense).

This is without getting into other considerations like how Netanyahu is a scapegoat for faux-progressives who want to deflect away from how this genocide has enthusiastic support from many powerful institutions within Israel. It is an Israeli project much more than Netanyahu's personal project.

P.S. Assassinating Putin wouldn't end the war in Ukraine either (nor would assassinating Zelensky or Biden)