This research presents a comprehensive link budget analysis framework for next-generation Low Earth Orbit (LEO) satellite constellations, designed to facilitate seamless and high-speed transcontinental communications. As global demand for low-latency broadband increases, optimizing satellite links under dynamic orbital and atmospheric conditions has become a critical technical challenge.Key Technical Contributions:Comprehensive Link Modeling: Integration of free-space path loss, rain fade, and atmospheric attenuation models within an ITU-compatible framework.LEO Optimization: Analysis of link margins for LEO constellations to ensure consistent connectivity across geographically dispersed areas.Adaptive Strategies: Investigation of adaptive modulation techniques and optical inter-satellite links to enhance data throughput and reliability.Environmental Resilience: Development of climate-sensitive attenuation forecasting and interference mitigation strategies to maintain robust link performance.The study concludes with strategic recommendations for spectrum agility and orbital stability, providing a vital roadmap for engineers and satellite operators building the future of global telecommunications infrastructure.