The 3 days Java Sea battles were more of a disaster for the Allies than Pearl Harbor. The true nature of just how bad it was, was kept hidden until much later in the war.
5,000 Sailors killed, a dozen plus ships sunk, including an Aircraft Carrier/Seaplane Tender (U.S.S. Langley) and several cruisers, Java and it’s oil lost, and India, Australia laid bare to attack, with literally nothing left in theater to stop the Japanese.
The propaganda of the time downplayed the importance of the losses, when in fact, the exact opposite was true.
The entire Allied campaign in South East Asia from December 8th through the fall of Burma was a massive disaster from beginning to end.
-Poor land commanders in the Philippines and Malaya.
-Lack of coordination between the services. (Both US and Commonwealth)
-Lack of coordination between the ABDA powers
-Inadequate Air Forces and poor use of them.
-Naval Forces thrown away piecemeal
The Japanese plan should not have worked, but outside of the Philippines it worked perfectly. They used their few advantages (morale, initiative, and air power) to hammer the Allies repeatedly and keep them off balance. Despite the fact that the Japanese were using barely enough forces to do the job.
The only bright spot was the Philippines, which held out longer than anywhere else, and would have held out even longer had MacArthur not screwed up their supplies.
Fortunately for us, 1942 was the last time a US or British forces would suffer such a comprehensive defeat.
(Yes, we lost at Kasserine Pass, but it was not a defeat on this scale.)