I read this story, the second in a series, in the mid-to-late 90's. The story follows two teens, male and female, who are attempting to cross the USA to get the boys family, hoping they have survived, following a nuclear exchange.
The main plot points that I remember is that they need to cross a river (frozen?) and the girl falls in and is saved by the boy, which improves their relationship. At some point they come across an old-timer/survivalist who is initially highly suspicious of the two and there is a confrontation in which he's injured. The pair go back and care for him and, in exchange, he teaches them how to use a bow and arrow. The group runs afoul of a group of raiders, and in the ensuing fight the bows prove decisive.
The book ends after the fight with two deciding to carry on to try and find the boy's family and the old man offering them safe refuge if they fail to find them and need a place to stay.
I also recall the cover as having red trim and showing the two characters with the bows and arrows.