Although regions are becoming increasingly important in the liberalization of international trade, the academic literature has only explored the issue extensively in the case of the European Union (EU). With respect to other regions, little is known of the internal factors that enhance their external performance. This paper uses EU interregional trade negotiations to examine the factors within the EU’s counterpart region that contribute to regional cohesiveness and facilitate the conclusion of an agreement. By applying the crisp‐set qualitative comparative analysis method to the 13 available cases, this paper finds that the external performance of other regions is not achieved through a combination of homogeneity of state preferences and strong institutions, as the EU literature suggests. While one or other of these factors may be necessary, they only work in conjunction with a favourable power distribution, that is, regional systems formed by a large hegemon and/or small open economies.