This dissertation is a study of US foreign policy that aims at maintaining its regional hegemonic status and preventing the emergence of another regional hegemon by implementing the offshore balancing strategy. US intervention during the 2003 Iraq War, strained US-Iran relationship, and the establishment of the Islamic State of Iraq and the Levant (ISIL) in early 2014 compel a reevaluation of US foreign policy. Two major claims of this dissertation include: (1) US foreign policy is consistent with offensive realist theoretical claims; and (2) US foreign policy is characterized by continuity when it comes to issues related to America's strategic interests. Utilizing a case study and comparative case study methodology, this dissertation outlines the following findings. The first finding of this dissertation is that US foreign policy actions under the Bush Doctrine, which led to the 2003 Iraq War, were dictated by the anarchic status of the international system, the possession by Iraq of military capabilities that could harm or destroy America, fear from and suspicion of Iraq's intentions, the need to ensure survival in an anarchic system, and the need to maximize relative power vis-à-vis other states. All these factors led to three main pattern of behavior: fear, self-help, and power maximization. Because there was no other regional great power capable and willing to balance Iraq, the US was forced to rely on direct balancing by threatening Iraq to take military actions, creating an anti-Iraqi alliance, and maximizing its relative power by destroying Iraq's military capabilities. Second, US foreign policy under the Bush Doctrine was a continuation of the 20th century foreign policy. US foreign policy during the 20th century was dictated by three major patterns of behavior: fear, self-help, and power maximization. In realizing its foreign policy goals, the US had to rely on buck-passing and balancing strategies. Whenever there was no regional great power able and willing "to carry the buck", the US would rely on direct balancing by either threatening the aggressor, creating alliances with other regional states, or utilizing additional resources of its own. Four major presidential doctrines and related occurrences were utilized to test the claim: the Roosevelt Corollary, the Truman Doctrine, the Carter Doctrine, and the Reagan Doctrine. The last finding of this dissertation is that US foreign policy toward Iran constitutes continuity and is dictated by US need to maintain regional hegemony by acting as an offshore balancer. In addition, the US and Iran share mutual strategic interests in several occasions, and a strategic win or loss for one state is a win or loss for the other. Like that of the US, Iran's foreign policy is guided by rationality. The Iran-Contra affair, the Armenia-Azerbaijan conflict, and the Russia-Chechnya conflict support the claim that Iran's foreign policy is based on rationality instead of religious ideology as argued by many scholars. Also, the 2001 Afghanistan war, the 2003 Iraq war, and the establishment of the ISIL support the claim that the US and Iran share mutual strategic interests. Cooperation is often desirable and in some cases inevitable. Despite this strong claim, US-Iran relationship has its own limitations because neither the US nor Iran would accept a too powerful other that could establish absolute dominance in the region.