Iraq and Libya
"When it comes to Libya, unlike Iraq, the country actually does have a history of twentieth-century federalism as well as complete territorial fragmentation. During the first years after independence, from 1951 to 1963, Libya had a federal state structure which among other things featured extensive taxation powers for the three federal regions (Benghazi in the east, Tripoli in the centre-north and Fezzan in the south). That tripartite federal structure, in turn, was based on complete administrative separation in the 1940s, when developments in the Second World War and the ouster of the Italians in 1942 had led to the creation of three separate zones of occupation with their own administrations. Although the ethno-sectarian geography of these lands did not correlate perfectly with the tripartite administrative configuration, Benghazi stood somewhat out thanks to a strongly influential puritan Sufi movement (the Sanusiyya), whereas non-Arab (particularly Berber) influences were said to be somewhat stronger in the west and the south. In contrast to the situation in Libya, Iraq remained a centralised state from the formal inception of the monarchy in 1921 until the beginnings of experiments with Kurdish autonomy in the 1970s.
"On the other hand, though, if we go further back in history, the parallels between Iraq and Libya are quite striking. Just like the territory of modern-day Iraq was administratively unified for a great deal in the late 1700s and the early 1800s, a political entity almost perfectly coterminous with the modern state of Libya existed in the same period: The Barbary state of Tripoli. Contemporary accounts of North Africa in the early nineteenth century almost invariably focus on four dominant political entities in the region: Morocco, Alger, Tunis and Tripoli. Headed by the Albanian Karamanlis – a group of military officers that broke with the Ottomans and as such another parallel to Iraq where the Georgian mamelukes reigned – the Tripoli state engaged in lucrative piracy activities in the Mediterranean that enabled it to subjugate, albeit tenuously, the territory to the south and east of Tripoli (incidentally, those piracies also brought them into conflict with the United States). After the Ottoman reconquista in 1835 (the timing being another Iraq parallel) that same geographical area remained mostly unified as a single vilayet until the 1880s. At that point, Cyrenaica was definitively separated as a distinctive unit. By way of contrast, Iraq oscillated between unified rule and various subdivision formulas throughout the nineteenth century...
"This point in turn relates to what is perhaps the greatest contrast between Iraq and Libya as far as territorial stability is concerned: Whereas both Tripoli and Baghdad presented a certain degree of continuity as proto-capitals for greater Libyan and Iraqi regions between the 1700s and the 1900s, Libya experienced a unique degree of both informal and formal territorial fragmentation during the first half of the twentieth century – above all as the result of different legacies of interaction with foreign, imperial powers in different regions of the country. Firstly, Sanusi resistance against the Italians provided for anti-colonial sentiment that translated into regional patterns: Cyrenaica, anti-Italian; Tripolitania, less so. Later, as the result of developments in the Second World War, formal fragmentation ensued in the shape of three different zones of occupation: Fezzan (French), Tripolitania (British), and Cyrenaica (separated from Tripoli and reconstituted as a single entity under the British, with special guarantees for future independence)."
I've excerpted only a few points from a post worth reading in full examining the possible parallels between the idea of a united Iraq and a united Libya. One thing I do wonder is the impact of economic integration in both countries. Tripoli and Cyrenaica may have had a common ruler around 200 years ago, but that wasn't a state that much penetrated society, nor was it particularly lasting. More important would be the extent of conquest in Libya by the Tanzimat-period Ottoman Empire, which I'm not sure about. The issue in both cases is that, economically, Tripoli looked west and Cyrenaica east, without much intercourse between the two halves of the country. The late Ottoman Empire would have brought similar administrative and educational structures to those areas, which would matter some.
This is not, however, to disagree with Visser's main point that Libya, as with other modern Arab states, is much more durable than those looking for social cleavages and supposed natural boundaries might suspect. Again, economically, a key to this is the expansion of the distributive oil state over the past 50 years, which brings everyone into important relationships with the central authority. More importantly, in the Arab world as a whole, the push has been to combine countries rather than break them up. Qadhafi certainly pursued many unity schemes, and I doubt public opinion differs on this particular issue, even if no such schemes are really practical.