In a situation where national infrastructure and life sustaining resources are suddenly cut off , population density will have a lot to do with how well you get by in the days following the crisis. When it happens, what you have on hand will likely be all you have to work with for an extended time. Those that lack supplies will seek out and take what they need in an increasingly hostile manner as time goes on. This is why being in a large city will likely be hazardous to your well being.
Very few will argue that being in a rural area when something catastrophic happens will greatly increase your chances of survival. A lower population density and more available natural resources to help you get by will make long term survival much easier. This is why so many people advocate heading for a rural area when something happens. The problem is unless you are already established in a rural area, survival will not necessarily be easier.
Source: News To Me