Agree 100% with this. US had 2 fighters that had the performance to do the interceptions, the P38 and the P43. The P43 had the speed and altitude performance to do the job, 4 50's would have been fair since 2 were synchronized lowering the rate of fire. Armor was supposedly added to them, but the whole wet wings that leak fuel even on the ground would have been a MAJOR problem. Too bad. If the P43 would have had self sealing tanks it could have been useful against Japan early on. The P38, even the early models, I think would have been a great choice. Great climb, 75 mph faster at high altitude than a Zero, 4 50's and a 20mm concentrated in the nose. I think 40 P38's would have ended the Darwin raids in a hurry.
The early P-38 was not a good high altitude fighter:
P38 at high altitude