The dramatic irony of history
Because this memoir takes the reader through well-known events in history, the drama is built through dramatic irony, because even though the reader (possibly) knows the events that unfold in front of Jeanne's horrified eyes, she doesn't have any advanced warning. To her, there is no predicting any of the unfortunate events, not the Japanese attack on Pearl Harbor, not the Japanese internment camps, and not the difficulties of Manzanar.
The citizen-enemy
According to the paranoia of the government, Jeanne and her family are risky citizens. They are treated in a way that is doubly ironic. Firstly, it is ironic because she and her family are citizens who are thoroughly American. She and her family are mistreated for fear of espionage, but the family is genuinely American with no ulterior motives. Secondly, it is ironic because although America later stands up against the Holocaust and the antisemitism of Germany and Europe, they had Japanese families in camps at the same time.
The problems of Manzanar
The goal of the Japanese internment camps in America was not to give the Japanese-Americans a new place to live or something. The government merely wanted to remove them from American streets. This meant that upon arrival in Manzanar, the family walked into an infrastructural nightmare. The camps were stuffed with people with no amenities or infrastructure. This meant that they were instantly in a state of chaotic living where the memoirist remembers learning to fend for herself.
The damage of Papa
When Papa comes home, there is a tension that has been building through dramatic irony that is finally loosed. They don't know what life has done to him. They don't know whether he has been abused, humiliated, psychologically attacked—but all those are reasonable guesses. The damage that Papa demonstrates is telling. He has a drinking problem and he doesn't socialize. Whatever happened to him left him with social paranoia and a need for distance. He takes up gardening as an attempt at solace.
The military oath
The last thing Papa wants is to give his life to the military, but the government is pinning him as a Japanese supporter. The only way they will stop harrassing him and his family is to sign over his life and join the army. He signs it as a sacrifice for his family, and then as if he had chosen this fate for himself, his community rejects him and mistreats him, adding insult to injury. The government took their home, their safety, their future, and now, they have even taken the father.
