Since the emergence of the United States as the world’s superpower almost fifty years ago, the discourse on its imminent hegemonic decline has been ongoing for quite some time. The advent of non-traditional security threats especially after 9/11 vis-à-vis the deep-seated problems such as internal political polarization in the American homeland have casted doubts over the tenacity and persistence of US hegemony. This is further complicated, moreover, by the long-standing economic instability in the US-led global political economy. More importantly, the rapid economic growth of China and other emerging powers, traditionally considered as countries from the Global South, has also been quite suggestive of the receding power of American hegemony. For this, some have even argued that the days of American global dominance could be nearly over. Despite of the impact of the above-mentioned factors that could undermine the US hegemonic dominance, this paper is going to answer this question what is Iran’s role in decline of “American Empire”? The hypothesis is that the United States’ failure in confronting Iran’s power in the Middle East region has been one of critical challenges for its hegemonic position during the last two decades. In other words, despite of the US military capabilities as a hegemon power, it could not be successful to achieve its strategic goals in the Middle East region in particular Syria, Iraq, Yemen, Lebanon, thanks to Iran’s influence and geopolitical power of its , so-called, Crescent of Resistance. Indeed, Iran has been able to weaken the US military stance in the region and eventually challenge the latter hegemonic position. Research method is analytical- explanatory and data will be collected through library and internet resources.