It was written in English. I read some of this by 2014 at the latest in British Columbia, Canada when I was in middle school in Grade 6-7. It could have been a series, or one book. I don't remember the cover. The protagonists are young adults, and so the book was probably for young adults.
The setting is a post-apocalyptic/heavily resource-drained world, with the narrative taking place in the United States; I don't believe the author explains why the world has gone downhill. The government barely retains some control, but many places are wild.
I remember some distinct scenes.
At the beginning, or maybe the beginning of the second in a series of books, the characters join a walled community, they regret it, and now they plan to run away through the sewers. They have some argument about leaving behind someone who is not fit to travel, or who doesn't want to leave. When that community finds out they've fled, they quickly assemble a group to chase after them into the forest. A member of the search group is described briefly as "gung-ho" I think it was the first time I saw that word on paper. The chased protagonists are then split up into 2 groups, who manage to escape. They planned to meet at Salt Lake City in case of this, I believe.
In a later scene with one group of three protagonists (2 male, 1 female), one or both of the male characters use up a bunch of food, including a bird he's killed to have a Thanksgiving celebration in their cave shelter. The third female is happy about the celebration, but also questions their sustainability. They later travel down the road.
In a later scene, the previous three are captured by a biker gang who have taken up residence in a zoo. The leader of the gang is like a king. Most of the animals have been eaten by the gang already. They plan to feed the two captured males to the alligators whilst the female becomes one of the slaves to the gang's leader. They take her to have make-up and different clothes put on. Another slave-girl gives her a tip "not to cry" when he rapes her, because "he hates that".
In a different scene, the other group of two protagonists (1 male, 1 female) are walking through a city (Salt Lake City maybe) and a 'peacekeeper' asks them why they aren't in school. The boy is worried about them not having a passport. He lies to the guard that they are "young lovers who have recently gotten engaged". The peacekeeper feels some sympathy and lets them go.