They did back in 1942 also. Only when Hitler attacked the USSR, his ally in invading Poland, did they do a 180 and support US entry into the War.
Germany (Hitler) attacked the USSR (Russia) June 6 1941 not 1942! They did their backflips when that happened. Though I grant you many are mentally slow in Hollywierd for some it could have taken 6 months to figure out what to do.
Support? they demanded that the US fight Germany immediately and open a second front to take pressure off of the Soviets.
The Communists still ran/run Hollywood and movies like Dr. Strangelove and Fail Safe depicted our Air Force inadvertently nuking the USSR and the horrors that followed. These movies coincided with the Communist-directed "Ban the Bomb" movement and supported their premise that only the US should give up "the Bomb".
In the mid-60s, the Ban the Bomb movement morphed into the "Anti Vietnam War" movement and they even kept their symbol which overnight became the "Peace symbol".