'The truth must always be attended by a pack of lies.' (Or something like that) -Winston Churchill
Take that, Britain!
So, we have better fighters, but they can build a shitload more? And what about American Mustangs, or something? Do they ever make an appearance?
The Allies, especially Britain, ran a "Europe First" policy. Due to it, most of their resources went to the ETO, apart from (most) Navy stuff. The first Mustangs were actually pretty bad fighters, fairly long ranged but less than impressive performance other than at very low altitudes, and the Merlin-engined P-51B appeared only November 1943. First examples make it to the Pacific Theater only March-May 1944 and the improved P-51D only July-August.
Apart from Zero the Japanese dont really have better fighters. Ki-43 is fairly OK in fighter vs. fighter but it lacks the firepower to be efficient interceptor. Ki-44 later in 42 improves the situation and its a much, much better in air combat as well, but it still lacks cannons.
P-38, P-47 and P-51 are all better than the Zero, but they arrive fairly late and in small numbers(until late in the war) and especially the complex P-38 is difficult to keep flying. Unique complex construction and 2 liquid-cooled V engines are not exactly optimal for primitive field conditions. Early P-38s had some fancy but very lethal(to its pilots) qualities too...
The USN Carrier fighter F6F Hellcat arrives in early 43, probably they have sufficient numbers of it by mid-43. Its better than Zero. But not that much better, pilot skill and tactical situation can give the Zeroes a victory, unless they are hopelessly outnumbered. Zero at least is still longer ranged, and the B5N2's range advantage over SBD Dauntless remains. Bigger problem is the F4U Corsair that arrived July-August 43, it will be the best Allied fighter then, and it can operate from carriers. We will see if the Allies equip their Marine squadrons with them or the carriers. Doubt they will have enough numbers for both until much later.
In theory, Japan's industry can be expanded to counter the US production, but what for? A thousand fighters can be built now and some ships more, but the war doesn't end in 6 months. Each factory expansion and repair costs resources, each aircraft as well, and planes and ships and ammo and equipment and supplies are needed later too. Not much use to have 1000 by then obsolete fighters in 1944, especially if the over-ambitious campaigns in the past have got the best pilots killed, the training was hurried and by then the pilots can barely take off.
Today, Kido Butai tries a different tactic. To my opponent it should seem that it is sailing North West north to Timor island, but instead it will turn south and be south to it at the dawn. No Zeroes will escort the bombers, I'm expecting a counter attack. If it doesnt come, well, since they dont have fighters in the area the bombers should (reasonably) safely sink some more US shipping.