In the event of a global nuclear war most of the humans will die, but the food potential of the land itself will be lowered too. Soil poisoned, machinery destroyed, animals killed. Without genetically engineered crops, irrigation, pesticides, fertilizer, and powered equipment, and the general lack of knowledge regarding simplistic agriculture, you're looking at 3000BCE level farming that we have to rediscover in one year. Many many more will die to starvation, and the violence that results from it. Hunting will be difficult due to low animal populations and people's general inexperience with hunting. And don't plan on canned food lasting very long. Anybody who's actually worked in grocery can tell you that our food supply is a constant stream moving through. It seems like there's tons of canned food because it keeps arriving on a daily basis by the trailer-load. Without farms growing the food, factories processing and canning that food, and without the road system and trailer rigs to move it around, canned food is going to dry up very fast.
Sorry. It would be extremely grim all around.
Not saying I wholly disagree with you, but you should read a book called
Nothing to envy..
It recounts true first hand accounts of an impoverished nation cut off from the rest of the world.
Mixed with factual statistics and what little media coverage there is inside the state.
Later on it goes through constant mass starvation, and situations that would make a quick nuclear war seem cheery.
Many starved themselves and their older sicker relatives to feed younger members, they ate grass and weeds for days / weeks / months.
Those few reports of canibalism, led to instant death sentences from the crowd not the state, years they went through this.
Their society may be different from many, and many others may resort to eating other humans, but the fact is many don't.
Many would rather starve and die then take that act.
It gives me hope thinking about it tbh.