How about transporting ground troops to garrison strategically important islands? These units were certified combat ready and sitting in California awaiting transport to the Philippines:
41st Infantry Division. Ship to Rabaul.
34th Infantry Regiment. Ship to Guadalcanal.
161st Infantry Regiment. Ship to Tarawa.
These transport missions, conducted with no enemy opposition during December 1941, would likely shorten the Pacific War by a year.
None of these formations could be considered combat ready in any sense of the word.
Moreover, it is simply untrue that there was no opposition in the areas wher you are proposing to send the formations.
In the case of Tarawa, they are in range of the anti-shipping units based at Kwaj and the Marshall islands generally. Whilst I dont doubt that the forces could get ashore, keeping them supplied would have been problematic. In the case of the 41st and the 34th Divisions, there simply was not the transport available at that time to undertake such a large sealift. In 1941 there was barely 500000 tons of shipping available, this had roughly tripled by the end of February. However it would have taken time to assemble and load these units, so it would probably be midMarch before the unit could sail.
If a more realistic lift is adopted and an RCT is sent in for these formations, they probably would have made it in time for Rabaul, but lacking any sort of proper taining, or Jungle skill, they would have been bagged with ease. The Japanese had already demonstrated the ease with which untrained troops could be dispatched by their seasoned veterans, and ther is nothing to suggest that these green formations would have done any better at all. The RCT that was already there could not stop the Japanese at that time, and this formation had far more experience than eithe the 34th or the 41st.
And supply of these formations would have been well nigh impossible, and would have placed the inexperienced US fleet, particularly her carriers at great risk whilst undertaking the deperate re-supply efforts that would have been required. And even Guadacanal would have been under sever blockade, with the Americans enjoying none of the advantages that the airfield and secure (relatively) supply lines gave their troops in August.
Far from shortening the war this strategy would have lengthened it. Instead if sending these formations off to be trained as they needed to be, they would have been thrown into battle green, and in all probability lost, along with a sizable portion of the US fleet as it tried to resupply and support them. The later campaigns in NG would have faltered and possibly stalled by their absence.