The allies could of ended the U-boat war much earlier.

[goggles]

as others have stated all the allied bombers did was drive the germans underground and force them to become more effcient with the materials they had

that being said...

allied bombers did indeed strangle germany the destruction of synthetic fuel facilities was a death blow to german military efforts the luftwaffe didnt have enough fuel to protect the factories, the heer had no fuel to shunt thier king tigers around and the u boats had no fuel to go on patrol

another nail in the coffin was the destruction of germanys railway infastructure it was being bombed faster than it could be repaired and rail was the primary means of transporting raw materials to the factorys causing crippling shortages

another valid point is the fact that germany did not moblize its women for the factories when the men left for war leaving them desprately short of skilled workers(the germans often sent engineers and scientists to the front rather put them to work in design and constuction) which lead to ever incresing dependance on slave labor and with an increasing number of workers being made homeless by bombing raids fewer and fewer showed up for work

the end result of fewer and less skilled workers greatly exagerated existing design flaws in late war designs the main reason late war tanks were so unreliable was partly due to sabotage by unwilling slave larborers and poor workmanship(cigarette butts jammed in oil galleys, teeth deliberately chipped off gears)

had germany taken the british or american approach to mass war production the war would have certainly dragged on longer and german victory would ahve been a possiblity