2) the end of the Ice Age
Europe, India and Africa.
The answer is '4'.
The Soviet economy crumbled further due to the heavy military cost of the invasion.
The U.S. provided financial support to push them out and shorten the conflict. The Red Army did suffer a loss of face but the collapse of the Soviet Union happened because military expenses drained their economy to such an extent that normal, everyday expenses could not be met.
The biggest one would have been when the US declared war. Other than that, it would have probably been the draft. I cant really think of others that would have influenced everyday life.