Hypothetically this could allow reinforcements & supplies to filter through to Mindanao before the primary US ground force in Bataan is eliminated. The Japanese could eliminate the outlying US garrisons/PI Army regiments, but its resources expended to do so. If they don't some PI infantry regiments acquire arms and at least a few months of training. More important is Allied aircraft filter into the Mindanao airfields and harass and bleed away Japanese strength.
With Singapore intact the remaining British blue water submarines fan out into the S China Sea, Yellow Sea, & beyond, picking off Jpanese cargo ships and the occasional warship. Getting a IJN carrier laid up for a couple months repair at this point means a lot. It also enables the RN ro raid into these seas as the USN did, with carriers or surface ships. The 8th March dispersal of a Japanese convoy near Lae bought time for the Australians in New Guinea. The RN might do the same for the US by raiding a Japanese supply convoy to Luzon.
there wis also the question of how much in naval strength the IJN loses in the course of losing the southern campaign. Did the failure to take Java or Sumatra include the Akagi or Hyriu settling to the sea bottom?
Politcally this forces the Jpanese leaders to face their true situation far earlier. Without the hope of the Allies rolling over and giving up to Japanese economic demands by the end of 1942 the Zaibatsu will be in a panic. With the Strike South strategy discredited, and probably the Navy as well, or worse the Army, Tojos government will be out & the new cabinet consider their negotiating position for peace.
This situation means a smaller emergency surge of war material to the Pacific threatre in 1942, and less in 1943. No S Pacific offensives on the scale of OTL, smaller preparations for the Central Pacific offensive in 1943. This leaves a bonus of cargo shipping for use to the ETO/MTO in 1943, or even later 1942. More aircraft, more amphibs, more ammunition, more ground combat forces to the ETO/MTO. In 1945 that effect is huge. Its possible Operation Anvil would be executed in early 1944 as Eisenhower wanted, the Op OVERLORD can be executed earlier, that the air offensive against Germany builds up sooner.