That's actually a good point. As I've been saying, if 90% or heck, even 70% of the population is gone, it would be very hard to reorganize. People would, but since they would probably be so spread out they would most likely form small city states.
Honestly, look at the Greeks and the Romans. Both civilizations much more advanced in terms of technology and weaponry compared to the rest of the world, but collapsed in a realitively short amount of time.
But really, a lot of it would depend on who survives the aftermath. As I've said, it's all fine and dandy that we still have technology and medicine, but if you don't have the people that know how do adequately use these means...it could mean big trouble. One of the biggest population killers hundreds of years ago was not war, it was disease. Without people trained in how to use medicine, (or with anyone to make more antiobotics and medicines once stores run low) a large percentage of the populace would die off each year from sickness alone. That happens in third world countries today.