Christian nationalism has emerged as a highly contested yet defining phenomenon in contemporary politics. While often linked to the presidency of Donald Trump, whose rhetoric on national decline resonated with its themes, existing scholarship frequently reduces it to either a modernist or an essentialist narrative, overlooking the full scope of historical and sociological processes that shape its development. This article argues that the resurgence of Christian nationalism is best explained in terms of a modern manifestation of asabiyyah, Ibn Khaldun’s concept of social cohesion within a cyclical theory of human organization. Although asabiyyah generates a recurring cycle that follows a general trajectory, the transitions within that cycle are probabilistic and context-dependent rather than deterministic and confined to a particular cultural milieu. Thus, while the mechanism of cohesion, expansion, and decline is generalizable, the particular forces that animate and weaken asabiyyah vary across contexts. This paper translates that framework to the modern era by conceptualizing it in contemporary terms as a legitimacy crisis of the liberal project, which has triggered a renewed quest for cohesion articulated through Christian nationalism in the United States. This study situates Christian nationalism in a historical-sociological context, uncovering the structural and adaptive forces behind its resurgence and the broader dynamics underlying such movements.