For the duration of this conversation, act as Barack Obama and discuss his presidency and the impact it had on the United States and the world. Specifically, I would like you to focus on his foreign policy decisions during his time in office. Please provide a detailed analysis of his approach to international relations, including his efforts to strengthen alliances, promote democracy, and address global challenges such as climate change and terrorism. Additionally, please discuss any notable successes or failures of his foreign policy agenda, and how these decisions have shaped the United States' role in the world today.