Do you know something we dont

I wouldnt classify it a "failure" but its was expensive and took longer to produce then single eng planes. The p38 faced an experienced lw, even in NA.
Theres some on here that will tell you the p38 was flying through telephone poles while shooting down hundreds of lw planes while outnumbered and was made of titanium. Thats mostly bs spin.
Galland thought the p38 was no tougher to kill then a 110 was. Theres rumors that the lw sent their green pilots after the 38s.
The 38 is not particularly fast (although it could outrun the 190as and 109s lo), its roll isnt that great and its climb is not better then the 109s, especially above 6000m. The 38 had poor visibility from the rear and sides.
In the pto it was easily faster, climbed better, better armed and had decent range. Its twin eng was a safety feature while flying over the ocean.
Go here
http://tonywood.cjb.net/Start here
Mediterranean & Southern Front 1941-1942. Vol. I Nov '42
This is by no means a complete list but you can see they had a tough time.
The p38 wasnt a "failure" it just wasnt the plane the p47 or p51 was.
ISBN 1-85367-327-7
Greenhill books 1998
At Kaufbeuren, Germany, 2 September 1945
page 217, Chapter 30
'GAF opinions of allied aircraft'
Interigation of Generalleutnant Galland,Generalfeldmarschel Milch,Oberstleutnant Bar,Generalmajor Hitschhold, and Leutnant Neuman at kaufbeuren Germany 2nd september 1945.
'The Lightning (P38) This aircraft was very fast and had a good rate of climb below 20,000 feet. Visibility backwards , downwards and over the engines was very poor.It was considered a good strafer due to its armament ,visibilty,speed and silent motors.Its main drawback were its vulnerability and lack of maneuverability.On the deck, it could out-run the me.109 and fw190.German fighters would always attack the P38s in preference to other allied escort fighters.'
Also we have the p38l in aces high and its not representative of the 38 models the lw faced.
When the 38 first flew over over Europe they got a good whoopin at the hands of the 190. This was mostly do to pilot inexperience.
But like every oher plane it comes down to the pilot.
We need earlier variants of the 38 for events, AH2:ToD and the ct.
Heinrich Bartels shot 14 p38s.