This article highlights a systemic aspect of the liberal peace that has been underemphasized by the existing literature. It argues that the liberal peace is constructed in part by the active efforts of a variety of liberal states and international organizations to promote democracy within states. This article examines the collective defense of democracy regime in the Americas to illustrate this political dynamic and applies Immanuel Kant's original formulation of the liberal pacific union to understand the contemporary inter-American system. The combination of a stronger Organization of American States built on a liberal democratic consensus among member-states, increasing trade interdependence, and a more liberal regional hegemony has transformed the inter-American system. One of the principal manifestations of this enhanced liberalism is that states in the Americas have agreed to intervene collectively in the domestic affairs of member-states to ensure the continuation of democratic regimes. For elected leaders and economic elites throughout the region and US policymakers, this support for democratic rule reflects material self-interest more than liberal idealism. While this collective defense of democracy regime, codified in the 'Santiago Commitment' of 1991, clearly reflects the increasingly liberal character of the inter-American system, this regime also challenges the principled commitment to self-determination that was essential to Kant's original formulation of the liberal pacific union. We examine the regional response to the first three overt challenges to the Santiago Commitment, in Haiti (1991), Peru (1992), and Guatemala (1993) to show how the collective defense of democracy has become a crucial element of how liberalism shapes international politics in the Americas.