Had the P-51 not come along there would have been armed Spitfires over Berlin in 1944.
It seems to be a very common idea to mix the USAAF and RAFs wartime strategies and just call them "Allies". This is a mistake.
The USAAF and ONLY the USAAF had a long range daylight bomber strategy in the ETO in WW2. The RAF had a seperate but parallel strategy of night bombing which was eventually morphed into what was loosely described as the "Combined Bomber Offensive".
The USAAF was responsible for escorting its bombers. Not the RAF. The USAAF had the need for a long range fighter. Not the RAF. Not in daylight.
The RAF had no plans for a long range bomber offensive in daylight. Ergo it had no plans and no need for fighters to escort its bombers in daylight. That was a USAAF problem.
P-38s were over Berlin and if there was no Mustang P-38s would have continued on as the 8th AF Fighter Commands primary escort fighter along with the P-47 Thunderbolt. The P-51B did not see combat until December 1943. It was a late comer to escort duty but the USAAF already had not one but two fighters already doing the work. I see no indication that they suddenly would have converted to Spitfires in 1944. I am sure that the long range Spit was considered...it was...but that does not mean any sort of manifest destiny. Lots of planes were tested for all kind of roles they never flew.
...and saying the Spit could not fly to Berlin is criticising it for a role it was never going to be asked to perform...by the USA or Britain. It was a short range fighter interceptor and later fighter-bomber.
I also find it curious the notion somehow that Spits were an oddity in the fighter bomber role when the P-47, P-38, P-51, Typhoon and Hurricane did those roles and NONE of them were designed for it either...so why the Spit gets singled out? Anyways the record of the RAF and RCAF Spit fighter-bomber units in 1944-45 is every bit as good as any of the others despite some unsubstantiated claims to the contrary.
From the original article:
It took 13,000 man hours to build the airframe – for that amount of effort you could have two-and-a-half Hurricanes or three-and-a-bit Messerschmitt Bf 109s.
...The Hurricane took 10,000 man hours so maybe homey can get a math tutor. 13,000 not 25,000.
"Straw-man" the size of a T-Rex the whole muddled splotch of it.
Ltr.