Most people would probably die, long term.
If most of the population is still alive in the early days of the collapse, there are going to be massive food and water shortages, which will lead to a lot of death from both lack of sustenance and fighting. This is the key time to have your own personal stash of food and bottled water. Not having to scrounge early on raises your chances of living considerably, at least for a while.
Assuming you had a stockpile or you were one of the winners of the food wars, you've made it a couple months. Let's say that infrastructure (electricity and fuel) are gone and they aren't coming back. You need to get somewhere that offers 4 things:
- Easily accessible clean fresh water
- Climate that supports growing most foods and raising livestock
- Defensible boundaries
- Enough people to collect water, tend to a farm, cook/clean, and defend what you've got
Just these 4 things are hard enough, but you also have to get there if you weren't lucky enough to be living in a prime location. This is going to kill a majority of the people left, either from exertion, exposure, starvation, or murder on the open road.
Assuming you make it to a prime location that isn't already taken and you have the willing manpower to maintain your food, water, and safety, you have to basically restart a small society. You'll need to set up some sort of rudimentary government (even if it's just democratic vote on each issue) so that decisions can be made without chaos. You'll need to setup a law system to try and punish crime in your society. You'll have to come up with a growth plan to expand your borders to handle new births and immigrants (if you decide to accept them). You'll need to find someone trained in medicine to manage the health of your population. Hopefully this person knows how to create basic antibiotics - otherwise your population will die from common infections that were just an afterthought before the collapse.
There's a lot more you'll need to do to survive long term, but that's the basic idea. Everyone thinks they could make it with a gun and their know-how, but long term survival depends on a lot more than you and your own badassery. It's not just a coincidence that average life expectancy has increased dramatically with the growth of society and our bonds to one another. We take a lot for granted.
