It's no secret that the British attack at Taranto that severely damaged the Italian fleet was a major inspiration for Pearl Harbor. But what if there was no Taranto? WI Italy remained neutral, for example?
I'm assuming some Pearl attack still happens, as such would seem to be the only hope of actually defeating the US and since memories of their defeat of the Russian fleet at Port Arthur were still fresh. But I may be underestimating the impact of Taranto.
Still, if there is a PH how does the operation change? Certainly there's not that screaming example of a torpedo-plane victory to base a plan off of, but would the idea of a carrier-plane attack still be rather apparent? Or would a "big gun" attack be the plan, parking off of the mouth of the harbor and shelling old-school (and inviting more Japanese casualties)?