Since the Cold War, NATO enlargement has moved from a contentious issue in US foreign policy debates to an accepted plank in US strategy. What explains this development—why has support for enlargement become a focal point in US foreign policy? After first reviewing US policy toward NATO enlargement, this article evaluates a range of hypotheses from international relations theory and policy deliberations that might explain the trend. It finds that no one factor explains the United States’ enlargement consensus. Instead, pervasive US support for enlargement reflects the confluence of several international and domestic trends that, collectively, transformed NATO expansion into a lodestone of US foreign relations. Regardless, the development carries a range of consequences for US national security; although enlargement afforded the United States significant oversight of European security and political developments, it came at the cost of increased tensions and diminished flexibility with Russia, allied cheap-riding, and US overextension.

中文翻译：

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北约扩大和美国外交政策：创意的起源，持久性和影响

自冷战以来，北约的扩张已从美国外交政策辩论中的一个有争议的问题转变为美国战略中公认的一个问题。是什么解释了这一发展-为什么支持扩大成为美国外交政策的重点？在首先回顾了美国对北约扩大的政策之后，本文从国际关系理论和政策审议中评估了一系列可能解释这一趋势的假设。它发现，没有任何一个因素可以解释美国的扩大共识。相反，美国对扩张的普遍支持反映了几种国际和国内趋势的融合，这些趋势共同将北约扩张转变为美国外交关系的一块石碑。无论如何，这一发展给美国国家安全带来一系列后果。