Good point.
I've been mulling over that statement a bit, and I don't believe that the American left collaborated directly with Nazi Germany or the Japanese Empire. The American left did oppose fighting the Nazis until 'Barbarossa,' and American communists in our State Dept. manipulated American policy to facilitate Mao's takeover of China. In that sense they were collaborating with the Kremlin to advance international communism, which still buttresses LIMD's observation of the lefts consonance with the muz.