The dramatic reconfiguration of the international system has given a new impetus to regionalism and to the growth of regional awareness. One approach to the emergence of regionalism stresses the importance of external configurations of power and the dynamics of power political and mercantilist competition. It is certainly true that changes in the international configuration of power have been very relevant to the emergence of regionalism in the Americas. Although the pressures on Latin American governments are very strong, moves toward the acceptance of a more cohesive regionalism involve difficult dilemmas and problematic trade-offs between issues. An approach to the emergence of regionalist groupings views regionalism in terms of the functional response by states to the problems created by interdependence. Such ideas have some purchase as an explanation of the new regionalism in Latin America but principally in terms of US-Mexican relations.