It is impossible to say with absolute certainty what Europe would have looked like by 1960 if the post-World War II policies for economic recovery in war-torn Western Europe and the policy of containing communist expansion had not been formulated. Much of Europe from France in the west to the Ural Mountains in the East suffered horrific physical destruction from the war. The Truman Doctrine and Marshall Plan played major roles in stabilizing the continent and helping recipients of economic aid to rebuild and to provide care for the millions of refugees who lost their homes.
The main reason why it is impossible to know what would have happened in the absence of those U.S. policies is uncertainty regarding the intentions of the Soviet Union towards Western Europe. It is known that Soviet leader Joseph Stalin -- one of the most brutal dictators in history -- harbored certain ambitions regarding the spread of communism, in Europe and in Asia, but was also wary of provoking an attack from the West while his country was being rebuilt following the devastation from the German invasion of 1941. Stalin made certain tactical moves, like agreeing in 1955 to withdraw from Austria, designed to minimize tension, but at the same time provoked crises in Berlin, oversaw the coup that established a Soviet puppet government in Czechoslovakia, fomented communist insurgencies in the Balkans, and, in 1950, convinced North Korean dictator Kim il Sung to launch the invasion of South Korea that started a bloody three-year war.
The level of physical destruction wrought by the war was of such that countries in Western Europe rebuilding while dealing with massive levels of dislocation, disease, and political turbulence, all under the shadow of the growing tensions between East and West, would not have been able to grow and prosper as they did absent the economic aid and military protection provided by the United States.