I think it would depend on who's in charge in America at the time. There were quite a few Liberals who were fairly sympathetic to the Soviet Union under Stalin (although they were largely ignorant of Stalin's worst excesses), most notably Henry Wallace. Without the worst excesses of Stalinism they would be in a much better position to present the Soviet Union as a flawed but reformable, and ultimately progressive, political force. On the other hand, without Stalin and his purges, it's possible that the Communist movement as a whole is stronger and more unified, which in turn could provoke an even stronger anti-Communist backlash during the Red Scare.
Without Lysenkosim, and assuming that things go more or less as IOTL for China, the Great Leap Forward will be slightly less worse, although Lysenkoism was only one of many things wrong with it.