Yes, they need an excuse. And remember: last June war was started by Israel, not by USA.
USA state is a machine which works with laws.
They need a legal excuse to deploy USA military full power.
And they need good moral excuses to justify behavior to their people if the war end in disaster like warships sinking.
So Israel is the best scapegoat for all that.
Even the most powerful USA men can't do whatever they want, they need to deceive, create narrative and sow traps.
Iran is wise because is sovereign.
Israel acts stupidly because it's a vassal corrupt state.
So beware with rest of USA vassals, because treason and stupidity is hard to distinguish.
Expect all kind of stupid things by USA vassals (GCC, Europe, Israel) in the next war.