If we swapped out all (or some) the Spitfires and Hurricanes in 1939-40 with something equal to the P-38G of 1943, then sure. There's nothing inherently wrong with twin-engined fighters, provided they keep or exceed the power-to-weight ratio, high wing loading, top speed and rate of climb of the opposing single-engined fighters. Any deficits in low speed agility should be made up with advantages in top speed and heavier armament.
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The Mk.2 Spitfire of 1939-40 had a 1,175 horsepower Merlin XII engine. So, let's put two of these into a single-seat P-38 equivalent, with the best British superchargers then available. As it was, we did not see the British put two Merlins into an operational single-seat fighter until the postwar DH Hornet. I'd stay away from the Westland Welkin high altitude interceptor concept - we need the ability to mix with Bf 109s and Fw 190s. Maybe we should start here:
View: https://www.youtube.com/watch?v=F2tOq0qmNXI%5B/URL