This essay examines the historically anomalous nature of the contemporary US-led European security order in the context of other distinctive aspects of European history. These include the absence of a long-lasting hegemon since the fall of the Roman Empire, Europe's rise and global dominance, and its instigation of the two world wars which brought its own destruction. The essay argues that America's role as effectively a non-territorial hegemon allowed Europe largely to reconcile the 'impossible trinity' of unity, security and liberty which had previously eluded it. However, this anomalous and relatively happy period could soon end if, due to US internal political dynamics or a need to strategically prioritise East Asia, the American Leviathan withdraws from its function as Europe's security provider.