Drawing on a novel dataset of hazardous waste shipments among Canada, Mexico, and the United States, we seek to enhance dominant modes of understanding transnational trading and regulation at the scale of the nation-state. We argue that these, while valuable, are limited by methodological nationalism. This epistemological position identifies the nation-state as the most relevant unit of analysis in examining "transnational" phenomena. In the case of transboundary waste trading, tracking waste between nation-states has come at the expense of identification and analysis of specific sites within nations that receive hazardous materials or send them abroad, obscuring the ongoing proliferation of waste havens at a subnational level and related environmental justice concerns. Working against methodological nationalism entails an epistemological shift that we pursue in this article through a series of empirical, analytical, and representational practices. We propose three visualization tactics that undermine nation-centered imaginaries: (1) documenting waste havens within the understudied United States through identifying subnational sites importing hazardous waste for processing; (2) establishing connections through flow maps connecting importing and exporting localities transnationally trading specific hazardous wastes; and (3) analyzing the corporate networks dominating the transnational waste trade. We argue these tactics build toward an alternative conception of methodological cosmopolitanism that highlights alternative routes toward environmental justice.