By 'tribalism' I mean political organisation in terms of tribe, clan etc. - ie. a 'familial' style grouping that exists today in African and parts of the Middle East. My assumption is that in pre-modern Europe political organisation must have been of this form at some point. Are there any works which deal with this?
The example I'm thinking of which might be relevant is the wars of the roses in England.
EDIT - Ah I've found a single blog post dealing with the issue. The tldr is that the Catholic church aggressively worked against cousin marriages in order to consolidate its own power and wealth; leading to the weakening of tribes / clans.
EDIT2 - And here is an academic paper cited by the blog post - "Family Structure, Institutions, and Growth: The Origin and Implications of Western Corporatism".
EDIT3 - Blog post about tribes in Anglo-Saxon England.
This is a whole book about the topic. James frequently identifies tribalistic tensions within current or nearly-current contexts and says much, much more about it than is worth summarizing here. The tribalistic context is deeply a part of ancient political culture, and a significant aspect of the organization of the nation-state. The tribe is distinct from the state in that the tribe is bonded by cultural affinities while the state is a creation of legitimacy and force that has power outside of culture.
James deals with the issue at length with the transition from kingdoms and early empires to nation-states. For him, the kingdom is still largely tribal, still grown out of familial and cultural relationships, and the new form of political organization arises when formal dynasties ended. I don't know if I'm convinced by his argument, mostly because I detect a strong bias. But the book was enlightening for me in how deeply it describes the notion of 'tribe'.