Salva stops just before leaving for the airport because he realizes he is leaving his old life behind. Why does this particular place and moment make him have this realization in A Long Walk to Water?

After traveling for many hours to arrive in Rochester, New York, Salva is about to step out of the terminal doors for the first time in America. His journey has been a long one, waiting in a refugee camp for years before finally finding his name on a list of people going to America and traveling there to meet his new family. In this brief moment, pausing just a second before departing, he is overtaken by emotion.
Up until this moment, he had retained some connection to his homeland, as well as maintained a slight fear that he may not, in fact, find a home in America. Now, however, he was stepping onto American soil, and his new family was, in fact, standing there on the other side of the doors. All of this made the realization that he was leaving his home behind much more real, and it hit him hard.