Purpose: The re-occupation of Afghanistan by the U.S. troops and the Taliban gives many lessons to the security of the Korean Peninsula. As shown in Vietnam Communization, the poor Taliban troops beat the rich troops of the U.S.-backed Kabul regime, which lacks a will to fight and strategy. The purpose of this study is to discover the implications of the Biden administration s withdrawal from Afghanistan with a neoliberal perspective and its implications for security and denuclearization on the Korean Peninsula. Method: This paper analyzes the US withdrawal from Afghanistan with the theory of Radall Schweller s neoclassical realism and explains political implications toward the Korean Peninsula. This paper will examine four major domestic factors in neoclassical realism focus on nationalism, military ability to mobilize, the influence of domestic interest groups, and nationalism and ideology. It suggests four implications over security and denuclearization on the Korean Peninsula by using the theory of the Neo-classical realism s perspective. Results: First, the withdrawal of the U.S. from Afghanistan can be seen as an expression of shrinking nationalism stemming from the U.S. priority that has emerged since the Trump era. Second, the continued burden of the war due to the worsening financial situation in the U.S. due to COVID-19 and the fatigue of the accumulated war was a cause for the US to withdraw from Afghanistan. Third, to win the votes of the white middle class in the Midwest of the United States, known as Trump s supporters, President Biden decided to withdraw from the need to rebuild the middle class. Fourth, the U.S. Biden administration decided to withdraw troops to focus on checking China, an authoritarian regime, based on value diplomacy that values democracy and human rights. Conclusion: As the Biden administration put more weight on checking China, the declaration of the end of the war pushed by the Moon Jae-in administration has been put on the back burner. The end-of-war declaration pushed by the South Korean government is opposed by the U.S. government as it weakens the justification for the presence of U.S. troops in South Korea that is a strategic hub for checking China. The Biden administration is implementing a policy to actively intervene in human rights issues in China and North Korea, focusing on value diplomacy, and is tightening sanctions against those involved, worsening the atmosphere of dialogue for negotiations. South Korea needs quiet diplomacy to promote the peace process. The U.S. sanctions on North Korea are creating an atmosphere and cause for North Korea to provoke more militarily in the future, raising the need to maintain a military response posture to South Korea and the US.