In this research paper, the proposed link budget framework is an elaborate link budget analysis framework of a next-generation Low Earth Orbit (LEO) satellite constellations to facilitate seamless transcontinental communications. The paper examines the technical needs required to support high-availability broadband coverage on Earth in dynamic orbital and atmospheric conditions. It combines the free-space path loss models, rain fade models, atmospheric attenuation models, orbital mechanics, adaptive modulation models, optical inter-satellite links integration, and interference resilience in an International Telecommunication Union (ITU)-compatible framework. The results indicate that dynamic environmental modeling, dynamic transmission methods as well as propulsion-enhanced orbital stability are important in ensuring that link margins are consistent in geographically dispersed areas. The study also gives prominence to the need to incorporate climate sensitive attenuation forecasting, spectrum agility, and security-oriented interference mitigation in order to make the system more robust. The paper concludes with the discovery that the next-generation LEO constellations have the potential to scale to low-latency and resilient transcontinental connectivity in case it is backed by an integrated and dynamic link budget design methodology. This framework offers a technically rigorous basis to satellite communication systems in the future in the whole world.