This research examines the impact of social media on political mobilization through a comparative analysis of two distinct contexts: the United States and Egypt. By employing a comparative study approach, the research reveals how social media functions as a tool for political organization and advocacy in democratic and authoritarian settings. In the United States, platforms like Facebook and Twitter have facilitated sustained political movements such as Black Lives Matter, enabling ongoing civic engagement and policy influence. In contrast, Egypt's use of social media during the Arab Spring exemplifies its role in rapid, large-scale mobilization against an authoritarian regime. The study highlights that while social media significantly enhances political engagement, its impact is profoundly shaped by the political environment and cultural context. Limitations include a focus on select case studies and reliance on available data, which may not fully capture the breadth of social media's effects. Future research should explore additional countries, investigate long-term impacts, and examine the role of misinformation. This study contributes to existing theories on social movements and communication, offering practical insights for policymakers and activists navigating the complexities of digital political engagement.