The Spitfire flew 28,981 sorties in US service and the Beaufighter 6,706, for a total of 35,687 sorties.
Combat losses for Spitfires in US service were 191 and we lost 63 Beaufighters for a total of 254 losses.
Spitfires in US service had 259 victories and Beaufighters has 24 for a total of 283 victories.
In WWII, for fighters, the USA flew 927,460 sorties against Germany and 295,415 against Japan for a total of 1,223,875 sorties.
So the total contribution by US-operated British fighters amounts to 2.9% of all sorties, 1.9% of all combat losses, and 1.0% of all victories.