Bump for later.
Preliminary guess: a more agrarian society provided for stronger localism and family structure?
Yes, but the question that arises is "why?"
The non-specific answer is because empire is weaker in the agrarian environment. It is weaker because the meaner is stronger in his individuality, more responsible for himself, possesses a more firm and clear sense of fellowship with others, and holds a broader set of capabilities (closer to being self-sufficient). Let us examine each of these in turn.
Self-sufficiency
By its very nature the agrarian environment limits the packing density of individuals to what we might conveniently label as an "organic" or "natural" maximum. Compare with empire cities where due to the artificially boosted rate of individual specialization which in turn is due to the artificially pumped levels at which the division of labor is maintained. The higher one's level of specialization, the lower the rate of self-sufficiency because the mean human being is capable of developing expertise in only so many areas of concern and as they are driven to go ever deeper into increasingly narrow channels, the opportunities for broadening horizons diminish immensely.
Not to get too conspiratorial-sounding here, but I will add that it seems like no innocent coincidence that people have been culturally pressured to develop the habit of holding only the narrowest of interests. In addition, beyond those of their chosen "professions", most additional interests often prove to be of the most inane sorts. Take, for example, those whose "hobby" is network action games such as HALO III or whatever today's raging fad may be. I can personally think of few things as profoundly absent of merit than this obsessive drive to park one's overweight hindquarter into a chair for 4 hours or more per day. Even golf, otherwise useless as it may be, holds the benefits of providing some token physical activity.
From a particular standpoint the division of labor has been a great blessing. But as with all things in life it has a price. There are no free lunches. If one values freedom and self-sufficiency above the fruits that division of labor yields, then the practice of grossly channeling individual ability as narrowly as we tend to may be seen as a curse. I fall more in line with the latter and am fond of recalling Robert Heinlein's quip that "specialization is for ants". In my case, though, I stand more to the center in my belief that we are not constrained by a dichotomy of specializing or generalizing. The question is where to draw the line between the two. But I digress.
The more tightly packed are individuals into local environments wherein it becomes materially impossible for men to sustain their lives individually, the more they rely upon others to provide the means of that sustenance. There is nothing surprising there. If, for example, each man required 1/4 acre of real ag-space to provide himself with all of the various fruits, vegetables, and meats to live throughout a given year, it then becomes physically impossible for him to do so when he has been sardined into a 400 square foot cold-water flat with his family and nary a square foot of arable ground within 1/4 mile of his habitation. Even his water is provided by third parties. This man is as helpless as an infant in these regards because the moment the providers withdraw provision, he faces very real and very immediate trouble according to the law of threes: three minutes for air; three days for water; three weeks for food.
It took no feat of intellect for the tyrants of old to figure all this out. If you want power, bend circumstance to favor it.
Fellowship
Organic packing density can be readily observed as being healthier for the human being. There is less stress on the individual. In agrarian settings, the absence of these pressures combined with the more pressing practical needs of everyday living due precisely and in part to the lower degree of specialization of the individual and therefore the lowered level of complexity ("sophistication" some would say - bah) leaves people with a greater sense of freedom, all else equal. When people feel free to associate and cooperate with their fellows as they please rather than being forced into it, they are more agreeable to voluntary endeavors and enter and operate in them without resentment.
Consider the typical contemporary sub/urban American circumstance where people are literally forced, often under threats of state initiated violence, to "cooperate" with each other. There is often resentment, however veiled and suppressed it may be. Add to that the pressures not to express disagreement and you have a formula for slow self-destruction, which is not a formula to drive one towards feelings of fellowship with his peers.
Furthermore, there is the factor of institutionalized hypocrisy that rises perhaps as an inevitable consequence of this unnatural packing of human beings into tight spaces. A fine contemporary example is the use of the dreaded "N-word". Issues of moral judgment aside, people like what they like and feel what they feel, even when it is considered socially unacceptable (by whom, one wonders). When you couple that with the lop-sided inabililty to openly express oneself, nothing is added to the general social environment but more trouble. Today, black people in America are tacitly entitled to call white people "cracker" and make sweeping statements that often begin with "white people be...", most often of a disparaging timbre. A white man, on the other hand, making any such broad-brush statements about blacks is immediately attacked as a "racist" and cast as pure evil, literally deserving of a beating, maiming, and even death. The black one is free to vent his petty frustrations along a line denied to the white. This is not going to foster a sense of fellowship on either side. What the negro fails to understand is that he is equally altered by this circumstance, only less obviously so because he thinks he retains a right and therefore a power above and beyond that of his perceived nemesis.
In cities people live more closely and yet are emotionally and psychologically farther separated than those in agrarian settings, on the average. Outright alienation and fear are rife in many cities around the world. Even in Europe where we are told the people are so civilized, alienation lays like a rot just under the seemingly placid appearances. I've stayed in the cities of Europe and I have watched people very carefully. It is interesting to observe those places where gypsies are found, for with them crime is rarely far behind as my first hand experience has shown. I have watched such people openly assault others in broad daylight and the other people simply walk around as if nothing at all of note were happening. Alienation.
individuality
Lower population density and the associated pressures, the compositions of which can be very complex and I suspect grown in complexity as circumstance deteriorates, leaves the individual the space and opportunity to step back from himself and become more familiar with who he is. The circumstance itself places him in a more favorable position in the social mix, again all else equal, because he feel less a droplet within vast seas. He can be seen and indeed is seen by his peers and therefore by himself. People in cities often feel anonymous; mere atoms within huge blocks of cold and lifeless concrete.
Add to this the tyrant's incessant clarion to suborn to the needs of the many and it becomes no great surprise why people in such conditions suffer from terribly attenuated senses of self, which in turn explains in large part the oft observed hyper-inflated ego phenomena so indicative of morbid weakness in the individual. It is precisely because we are individuals that this artificially imposed demand that we suuborn ourselves in-toto to the collective, that we abdicate our senses of self in favor of the hive that such demands can result only in sickness and the rise of all manner of symptomatic manifestations. Place a fish on your dining room table and it is a foregone conclusion that unless rapidly returned to the water it is going to die. Forcing individuals to live, act, and think as mere cogs in a greater gestalt is a guarantee of morbidity because the condition meets nature with nontrivial violence.
Upshot
Compression of populations into small and unnatural spaces necessitates a strong division of labor, which necessitates morbidly high levels of specialization and further requires (often by force) the cooperation of individuals not as such, but as fungible units devoid of any true identity.
Is there really any question as to why cities tend to be sick and sorry places? The truly amazing part in all of this is the factor of human adaptability. People are so adaptable in psychological terms that they will acclimate to poisonous surroundings and come to accept and even prefer them despite the fact that they are being slowly destroyed in body and mind. The very sense of self-preservation has been bred out of these people and they will march headlong to their own demise if so ordered because of it. We see it every day.
The frightening thing in all of this, however, is the technological factor. In days past, the poisons of city life were kept mostly bottled up in such places, leaving the rural areas relatively unharmed. Today that is rapidly changing, what with the communications technologies that are now almost ubiquitous. The psychological poisons of empire are now rapidly spreading like contagion into all but the most remote areas and I do not believe it stands to produce desirable results, on the whole.
