ABSTRACT: Since the early 1980s, scholars have debated whether or not the converging forces of globalization have disembedded city-regions from their national contexts. This study explored this question through a comparison of post-1990 growth trends in the Detroit and Greater Toronto Area–Hamilton regions (GTAH), two urban areas within the same natural region and closely linked by industrial production flows, yet politically situated within two separate Federalist states. Guided by Nested City Theory, it reveals how their dissimilar contexts for race, local autonomy, and multilocal planning have helped foster divergent spatial patterns in the two regions. In particular, provincial controls governing municipal fragmentation, Ontario's Planning Act, and subregional/microregional planning have been key embedded structures helping to limit population decline and disinvestment in GTAH core cities. In the process, this article shows how urban trajectories have remained nested within multilevel spatial and institutional configurations. Its findings also call for greater consideration of nested state/provincial factors in cross-national comparisons of cities within Federal states. Finally, its conclusion offers a starting point toward a more nuanced specific version of Nested Theory to be called the Contextualized Model of Urban–Regional Development.