The Brits listed Oil targets even in 1940. They realized that --they-- didn't have the aircraft or doctrine to get them. Eearly on, the USAAF planners (along with the Brits) settled on a priority that was not very good. Heavy industry and U-boat pens proved very robust. But it wasn't until the bases in Southern Italy were captured and Ploesti could be savaged, that hitting Oil would be crippling. But the Americans missed the boat on targeting priorities and escort fighters. The bigs thought the B-17 combat boxes could go it alone and be flying buzzsaws on which to wreck the German day fighters. Seems like it was some assistant Secretary of War who came to visit in the middle of 1943 and was just appalled at what was happening. He got the ball rolling faster for the Merlin engine Mustang and just a general awareness that unescorted strategic bombing was NOT going to work.
There was a P-38 group in England in the summer of 1942, but Eaker or --somebody-- allowed it to be shifted to North Africa. That is a real shame. EVERY P-38 should have gone to England and its technical problems given the highest priority. Even a few dozen escorts made a big difference in breaking up German attacks. So the Americans had a steep learning curve. But at least they learned.
Harris learned nothing. He was practically a criminal.
Even in May, 1944, in just THREE DAYS the 8th AF cut German oil production 50%. Then they were switched on to invasion targets.
Had the enormous power of Bomber Command been added to the USAAF's, the war could have ended maybe in September, 1944.
Harris pretty much refused. He'd plead bad weather for precision bombing and wreck a city center.
Walt