The international collapse of communism and the implosion of the former Soviet Union have left the United States as the only superpower in the world. The Soviet Union's internal crisis had its roots in a long-standing disparity between the Communist system's areas of great achievement and the inadequacy of the general condition of the country's infrastructure. The United States came to the position of world primacy at a historical juncture characterized by many changes in the international scenario. The double rejection, among many other factors, could induce a closer cooperation between the two Americas. The Mercosur is, essentially, an extension of the Brazil-Argentina common market to the other countries of the Southern Cone. The new liberal fashion prevailing in the world today is reviving the old discussion on the advantages and disadvantages of economic liberalism for developing countries.