Very valid point. In fact the past 20 years have already proven your point many times over.
Austin has always been a liberal city, but they crossed the loony rubicon some time back and sane voices are no longer allowed to be heard. Dallas and Houston were traditionally conservative cities but today they are politically unrecognizable. I've even noticed some of the suburbs and smaller towns have turned to the dark side and believe more taxes and more regulations are the answer.
From a electoral college standpoint add up the votes in those three major cities plus the South Texas vote and things get dicey quickly.
Just an observation, but cities tend toward statism anyway. It starts off innocently enough. When there are enough people in a small area, you get a lot of different things that tick people off enough that you rapidly end up with a lot of rules. They see it as a coping mechanism, and people just stop talking with each other and let the rules and enforcers do the talking instead.
One or two bad incidents and people are willing (again, out of fear) to let more rules be passed to keep them feeling 'safe', whether or not the rules actually do anything to make them safer.
Next thing you know you have full blown liberalism.
Out in the sticks, people interact and get to know each other, there's a face on the person they deal with, and have more of a tendency to either leave one another alone (more space, less effect) or work things out if there is a problem. It becomes a point of pride to be a decent neighbor and help each other out in a pinch, instead of compound problems with rules and enforcers.
Those fundamental differences in lifestyle and approach remain a dividing line in political philosophy, with each drawing like people to their core or away from one. City folks revere the services and opportunities available in the very concentrations of population which cause them to sacrifice fundamental freedoms. Those less inclined to be subject to those rules or lifestyle and who find nothing attractive enough about those opportunities to forego the liberties of a more rural existence will shun the city and its rules, as much as possible.
At some point, a concentration of people reaches that critical mass when not all of the opportunities for commerce are benevolent: vices concentrate as well as virtue, and create markets for the particular subject thereof, far beyond that which would ordinarily be encountered in a rural environment. The resultant criminal activity compels more rules, more enforcers, and less freedom for the average person who perceives the need for more government as a result. When those concentrations of people can outvote the populations of the relatively huge swaths of land which surround them, they will make rules for the people who do not share their vision, and in effect create criminals where ordinarily there would have been no problem.
I think it has always been thus, and the damnation of every major empire in the past as urban centers took control overall.
