"So, explain again why the A6M2's thrashed the US version of it"
Easy, in its only air combat with the US it was outnumbered 118 to 26 at Midway.
7 F4Fs and 19 Brewsters vs 36 A6M2 Zeros (4 squads of 9) and 72 Attack a/c (36 Kate bombers and 36 Vals), the USMC put up a very tough fight, losing 19 of their # in the melee, fighting the Zero for the 1st time and knowing little about its strengths and weaknesses.
...that and I guess the Finns didnt ever fight the IJN? they fought Russian pilots with probably 1/4 of the training in hours (and thats probably generous), in a/c that were much less manueverable. The most inexperienced Zero pilot at Pearl Harbor had 1000 hours in fighters.
Kinda apples and oranges, some LaGG noob vs an A6M2 Zero naval pilot in a dogfight. Who you going to bet on?
That being said the Finns did remarkably in the Brewster, being both out numbered and in many cases out classed. I take nothing away from their combat record.