Ques-Do you agree with the view that formation of NATO marked a revolution in American attitude to the world problems? 

Answer: Formation of NATO was certainly a long way for a country that had traditionally been isolationist. But, if we look at the events since the end of WWII, then the NATO appears as a logical next step in the steadily building up Cold War.

Truman Doctrine (February, 1947): In response to the Greek Civil war, President Truman announced that it shall be the policy of USA to aid the free people against attempted subjugation by armed minorities.The American government adopted the goal of containment to stop the spread of communism. Truman Doctrine led to the creation of a set of global military alliances directed against the Soviet Union.

The Dominos Theory: The USA provided covert military aid to the French because a communist victory in Indochina would have precipitated the spread of communism throughout Southeast Asia. 

Marshall Plan (European Recovery Program): The United States feared that the poverty, unemployment, and dislocation of the post-WWII period were increasing the appeal of communist parties to voters in Western Europe. So, under the Marshall Plan, the USA gave $17 billion in economic support to rebuild European economies after WWII. The cohesiveness generated in the capitalist block by Marshall Plan was a key catalyst for the formation of NATO in 1949 CE. Soon, Truman signed the National Security Act of 1947, creating a unified Department of Defense, the Central Intelligence Agency (CIA), and the National Security Council (NSC). These would become the main bureaucracies for US policy in the Cold War.

The brutality of communist coup in Czechoslovakia shocked Western powers more than any event up to that point. It helped to spur steps toward collective security that would result in the establishment of NATO.

 Berlin Blockade and Airlift (June 1948- May 1949): In June 1948, Britain, France and America decided to unite their own German zones and introduced a new currency Deutschmark. The next day, Stalin cut off all rail and road links to West Berlin. The subsequent airlift led by USA showed American commitment to put up a global stand against communism.

Thus, United States, Britain, France, Canada and 8 other western European countries eventually signed the North Atlantic Treaty (April 1949), establishing the NATO.