The main conflict in Gary Paulsen's The Crossing concerns fulfillment of needs. Both Manny, the Mexican street urchin, and Robert, the American soldier, have their own needs. Manny's need is to not die of starvation but to instead cross the bridge from Juarez, Mexico, into El Paso Texas, the United States. Manny's conflict can be identified as self vs. society. Robert S. Locke's conflict is his need to forget all of the friends he has had to abandon to their deaths as a soldier in wars. Since society creates war, we can also call Robert's conflict a one of self vs. society.
Manny and Robert meet because Robert crosses the bridge each night into Juarez to visit the bars and drink himself into a state of forgetfulness. Eventually, Manny asks Robert for help crossing into Texas so that he might live. Robert agrees to help him, but before he can acquire papers for Manny, Robert is killed defending Manny from four street wolves, kidnappers who sell street urchins for profit. Before Robert dies, he gives Manny his wallet, telling him, "Take it and run and cross and get the green card and live there ... it is what you want ... what I want for you" (as cited in eNotes, "Extended Summary").
This is a perfect resolution to both of their conflicts of self vs. society because death frees Robert from the painful memories of not being able to help his friends in battle; plus, Robert is finally able to help someone in helping Manny survive.