Political revolutions fundamentally alter the course of a nation's history by challenging existing power structures and redistributing authority. These revolutions can arise from social, economic, or political grievances, leading to the overthrow of governments and the establishment of new regimes. Notable examples include the American Revolution and the French Revolution, both of which not only redefined national boundaries but also inspired global movements for freedom and democracy. The aftermath often results in significant changes in governance, societal norms, and economic systems, reshaping national identities.