Strayer argues that city-states and empires both had their problems, and that “The European states which emerged after 1100 combined, to some extent, the strengths of both the empires and the city-states. They were large enough and powerful enough to have excellent changes for survival – some of them are approaching the thousand-year mark, which is a respectable age for any human organization. At the same time they managed to get a large proportion of their people involved in, or at least concerned with the political process, and they succeeded in creating some sense of common identity among local communities. They got more out of their people, both in the way of political and social activity and in loyalty than the ancient empires had done, even if they fell short of the full participation which had marked a city such as Athens.”
We might add an insight from Adrian Hastings (The Construction of Nationhood: Ethnicity, Religion and Nationalism (1996 Wiles Lectures Given at the Queen’s University of Belfa)), who argues that this middling form of political organization (which he thinks begin much earlier than most contemporary historians would believe) drew their inspiration from Scripture: “The Bible presented Israel itself as a developed model of what it means to be a nation – a unity of people, language, territory and government.” Elsewhere, he adds, “The Old Testament provided the paradigm [of nationhood]. Nation after nation applied it to themselves, reinforcing their identity in the process.” Because they possessed the ark of the covenant, Ethiopians saw themselves as the “true, Christian, Israel.” So did everyone else: “Undoubtedly in Frankish eyes, the French were little less. And, in English eyes, the English. In Serb eyes, the Serbs. . . . Each people sees its ‘manifest destiny’ clearly enough.” Hastings knows that the concept of a “holy people” is “realized in a universal community of faith and by no means in one nation” but he observes that “for ordinary Christians, lay and clerical, that can seem too remote, too unpolitical.” We are likely to have to combat this heresy for a long time to come.
Why would a nation-state be any more inherently idolatrous than "a city set on a hill", or "vital Christianity"?