In August 1954, efforts to establish a European Defense Community (EDC) foundered in the French National Assembly. This was a severe setback for the cause of European integration, but it was not its downfall. The American supporters of European integration, too, continued to support its advancement in other areas; as Eisenhower wrote to his friend Walter Bedell Smith in September 1954: “We cannot sit down in black despair and admit defeat.”

By January 1961, when Kennedy assumed the American presidency, the European integration movement had reinvented itself around the European Coal and Steel Community (ECSC), which had become operational in 1953. In the wake of the EDC's rejection by French parliamentarians, most supporters of European integration had understood that it first had to be pursued in the economic realm; economic integration, they had judged, might then – through some kind of bottom- up process – pave the way for political and possibly military integration. The integration movement had been rekindled at the Messina conference in June 1955 by the foreign ministers of France, Germany, Italy, the Netherlands, Belgium, and Luxemburg, despite an atmosphere of gloom. It had reached a new milestone with the Treaty of Rome in March 1957, establishing the European Economic Community (EEC) and European Atomic Energy Agency (EURATOM). Importantly, the “Six” had also confirmed the political aspiration of their cooperation, as the Rome Treaty had declared their determination “to lay the foundations of an ever closer union among the peoples of Europe.” By contrast, the rival European Free Trade Association (EFTA) of seven other European countries (often referred to as the “outer Seven”), established in January 1960 at the initiative of the British government, had never been able to take on a life of its own. In fact, as Kennedy entered the White House, Prime Minister Macmillan was already actively preparing the grounds for British membership of the Common Market.

There is little doubt that the support of consecutive American administrations was vital to the European integration movement; this support was also actively solicited by its leading proponents (the likes of Jean Monnet and Paul-Henri Spaak). From the standpoint of its immediate self-interest, the United States might have been expected to prefer dealing with divided European governments that could be played off against another.