Public health data modernization in the United States has accelerated since COVID-19 exposed systemic weaknesses in fragmented data infrastructure and governance. Technical solutions have advanced, but legal and relational barriers still complicate data sharing across jurisdictions. Traditionally, interjurisdictional data sharing has relied on individually negotiated Data Use Agreements (DUAs), a process that is both resource-heavy and often opaque. To address this, the Centers for Disease Control and Prevention have proposed a Core DUA to standardize terms and reduce administrative burden. However, its success depends on trust — a fragile foundation increasingly strained by politicization, perceived lack of transparency, and controversial federal actions involving sensitive data. Jurisdictional concerns about compliance, security, and misuse underscore the need for governance frameworks that prioritize clarity, reciprocity, and accountability. Coercive approaches risk deepening fragmentation and undermining collaborative governance. Ultimately, modernization efforts will fail without supporting trust as the cornerstone of public health data governance. This article examines legal variation, transactional friction, and evolving jurisdictional perspectives to illuminate the critical role of trust in shaping the future of public health data systems.