Global infrastructure systems face rising sustainability risks despite unprecedented investment, revealing that performance failure stems more from governance architecture than from capital scarcity. This study examined how governance and resource context shape infrastructure project sustainability through institutional capacity and financial policy support using harmonized multi country secondary data drawn from internationally recognized governance, fiscal, and infrastructure performance databases. The research was necessary because prevailing infrastructure models privilege financing scale and technical design while under explaining why similar investments yield sharply divergent durability, continuity, and service reliability across countries. The study applied advanced structural equation modeling integrated with multilevel regression to capture both direct and conditional governance effects across heterogeneous institutional settings. The findings showed that regulatory coherence exerts the strongest influence on sustainability, followed by fiscal continuity and accountability enforcement, while institutional capacity and financial policy support amplify these effects by stabilizing governance transmission. The results demonstrate that sustainability responds to governance composition rather than governance presence, challenging dominant funding centered narratives in global infrastructure debates. This research model contributes through the addition of institutional transmission capacity as an internal governance mechanism, thereby broadening explanatory scope and offering a refined framework for understanding infrastructure sustainability in multi country public sector systems. The contribution advances global theory by repositioning governance as a causal architecture, informs managers on diagnosing binding governance constraints, and supports policy designs that prioritize rule alignment, fiscal predictability, and enforcement certainty. The study recommends shifting international infrastructure assessment and financing frameworks toward governance architecture diagnostics that anticipate sustainability risks before asset degradation occurs.