Americans joined the war late for understandable reasons. Unlike the Soviet leadership, we had respect for life — and that of our own soldiers included.
Stalin killed more Russians than Hitler. Remember that.
History has glossed over the fact that many killed in the USSR were part of what had devolved into a civil war along the western frontier. Many non-Russians there (Ukrainians and the newly kidnapped Baltic populations in particular) supported the Axis because they saw what the USSR was: Mass murder.