The USAAF tactics in 1942 as used in Borneo/New Guinea (SW pac area) did indeed suck. Sucked bad. But so did the IJAAF as they practiced a kind of one-on-one samurai type fighting. They may have arrived to the fight as a group but that's about as far it went regarding squad tactics with them. The IJAAF pilots most often did not even have radios in thier aircraft to save weight. Still, it wasn't just the IJAAF pilots, such as Sakai, who expressed nothing but comtempt for the P-39. Even the USAAF P-39 pilots wrote that they could not out run, outclimb, out turn nor out dive the Zeke. The P-40 could outdive it, or out zoom climb it if they caught it unawares and those were the P-40's saving graces.
Some similar thoughts on this by Baugher;
" The Airacobras operating in the Southwest Pacific were sometimes called upon to serve as interceptors, a role for which they were totally unsuited. They proved to be no match for the Japanese Zero in air-to-air combat. In fact, because of difficulties with the oxygen supply, the Airacobra was not even able to reach the Mitsubishi G4M (code name *Betty*) bombers raiding from altitudes above 25,000 feet. In the laconic words of the official AAF history: "The Airacobra, even in a good state of repair, was unable to meet the Japanese fighters on equal terms." Experienced Japanese pilots such as Saburo Sakai regarded the Airacobra as a relatively easy "kill". The P-39s were not as manauverable as the lighter and more nimble Japanese fighters, and enemy fighters could often avoid combat with the P-39s by outclimbing them"
And from Widewings web site:
..."Welch finally received orders to return to the Pacific. George reported to the 36th Fighter Squadron of the 8th Fighter Group in New Guinea. The good news was that this squadron had been seeing combat. The bad news was that is was flying the hopeless Bell P-39 Airacobra. Welch found himself flying mostly ground support missions, this being largely due to the P-39’s poor combat performance and its limited range. Certainly, the 37mm cannon was useful against ground targets, but the Bell was at a serious disadvantage when facing Japanese fighters. This was largely the fault of it being fitted with an Allison engine that lacked a two speed, two stage supercharger. This meant that performance dropped off quickly above 12,000 ft. At the altitudes necessary to engage the Japanese bombers and fighters, the P-39 was an absolute dog. Welch did not view the lack of performance at altitude as the primary sin of the P-39. What truly turned Welch against the Airacobra was its limited combat radius. With the majority of air to air engagements being fought beyond the reach of the Bell, opportunities to shoot down more Japanese were nearly nonexistant. Naturally Welch noted that there were squadrons on his base that were flying the P-38G Lightning. Now, here was a fighter! Fast, long ranging and equally important, its twin Allison engines were turbosupercharged. This allowed the P-38 to climb higher and faster than the P-39. It was everything Welch wanted and the performance of the P-38 was reflected in the tally of Japanese aircraft being shot down. George wanted the Lightning, he wanted it badly and cornered his group commander and inquired as to when 36th could expect to get the P-38. The answer was: “When we run out of P-39s.” That was all Welch and the pilots of 36th needed to hear. Virtually any problem encountered in flight (real or imaginary) resulted in a bailout from that day forward. The operational loss rate climbed dramatically. Welch found himself in hot water with the Group commander, who pointed out that George had been very successful in the P-39."
Remember, maximum level air speed is not the same as combat cruising speed. WWII Pilots did not run at military throttle the whole flight like we do in AH and other sims/games. So quite often comparing maximum level flight speeds is pointless.
Westy