I am no expert on the P-38 but I believe it did not suit European conditions very well, more so for what the USAAF wanted of it; a fighter.
Even though it had more success in the engine department in the Mediterranean and Pacific than Northwest Europe its combat record in both NW Europe and the Mediterranean was poor, especially in comparison to its record in the Pacific. The P-38 was a long range fighter that traded range, firepower and speed for manoeuvrability. This worked well in the Pacific Theatre where its superior speed, climb rate and fire-power decimated Japanese aircraft primarily utilising energy tactics
In the European Theatre its only advantages would be firepower (arguably) and range, a relatively comparable to the Me110 in the BOB. Had the Japanese developed better aircraft in the required numbers perhaps the P-38 would have not done so well, or further developed, or the USAAF abandoned bombing of Japan, or etc. (You can't second guess history only provide alternatives - war is a game of opportunity cost)
Nevertheless the P-38 was developed with this knowledge in mind so it did its job, and very well and that job was as a long range fighter in the Pacific Theatre - to which it was excellently suited
Just as an expansion and bringing into play my point about war as a game of opportunity cost I feel the P-38 would have been better utilised as a fighter bomber and Schnellbomber similar to the De Mosquito
Furthermore these aircraft should have been utilised as the backbone of 'Strategic' bombing in Europe
I love the big strategic bombers as aircraft like the B-17 etc but their usefulness in war could be questioned, perhaps built in the wrong era just like building a dive bomber today
especially looking at the success rate of strategic bombing (not bad but not great). Strategic bombing bar nuclear weapons has only become a viable alternative recently with the introduction of PGM's. Modern PGM's are beginning to offer increasingly viable platforms possibly becoming a better alternative but not replace missiles by large though saturation techniques ( HARM cost nearly $1m whilst a SDB costs $40K
. The RAF stated the Mosquito as 4.95 times more efficient than the Lancaster post-war. A swarm of such fast low level bombers would have over-saturated defences, delivered ordnance with far more precision than alternate methods, and if you follow the math causing 4.95 times as much destruction/success in strategic bombing minimum (likely much much more) all the while keeping Wehrmacht and Luftwaffe resources tied to fighters and Flak guns (again if not increasing requirements) with enough capital left over for increasing the size/capability of the invasion ground forces and logistics support
These things unfortunately usually get discovered after wars (ironic I know but hindsight is always 20/20) and it does not help when it was a result of bad decisions and political manoeuvring that can not be blamed on hindsight
There are many examples of this in modern warfare, historical, present and those yet to come. (The development of LGB's as a result of precision bombing needs in Vietnam for the USAF, the development of the AMRAAM as a result of the AIMVAL/ACEVAL exercises; multi targeting radars were useless if you did not have the ability to use them - this stuns me still today an example of poor foresight and waste of money. The lack of countermeasures against the SA-6 during the Yom Kippur War. The F-35 looks like another strategic mistake etc. I could go on all day with a long list so you will just have to accept this small list as sufficient evidence
On a related note the USSR did a bit better in this respect, they listened to their generals and soldiers and their requirements and for some reason despite widespread corruption within the general system corruption, backhanders and poor decision was some sort of taboo where the Soviet Armed Forces were concerned.
Please anyone feel free to correct me on the P-38 or anything else. Knowledge is power. And forgive me for this somewhat half history, half military science/economics lesson