Think of the Japanese arriving as a peace delegation, demonstrating their new DEFENSIVE technology of strike aircraft. Last time they arrived on a packet steamer, but this time, they brought 3 carrier groups so that all their brave sailors can admire the American might!
Americans and Japanese happily tour bases together, taking snapshots for their vacation albums and reviewing blueprints and base layouts solely to gaze at the majesty of the ordered rows of aircraft sitting in the open, what a sight to behold!
It seems less than realistic, but in the years just pre war, Germany officers were invited to Fort Riley, Kansas to see the primitive state of US armor doctrine development…. German and Russian officers exercised together under a non-aggression pact, the Japanese were allies so they were given quite a bit of leeway and a Japanese spy was place in an apartment right across from Ford Island, HI, with a telescope and a wireless set…in WW1 German spies blew up a New Jersey harbor but they had free reign because they were just neutral citizens, right? Germany was quite angry that the “neutral”! US was sending arms to its co-belligerents, the agents were fairly careful to destroy only pending arms shipments and not civilians…
You can tell any story to explain it that you want, but the real life truth is that until the shooting begins, everyone is supposed to be friends and many erstwhile allies (France? Italy? Japan?) are happy to flip sides between wars or bow out (UK/Cz/Poland alliance??) when it is in their national interest.