Henry Park is an incredibly complicated character; his facility with words and language is part of what has made him so successful in his job as a spy in the US, while in his private life the stoic silence he learned from his Korean father cost him his relationship with his wife Lelia, who is alienated by (among other things) his inability to articulate his emotions upon the loss of their son. It's tempting to reduce Henry to component cultural pieces (his "silence" is Korean, and his emotional and linguistic facility at work are "American"), but the story defies simple answers and checked boxes. Henry does come to believe that Korean men (or at least he and his father) “depend too often on the faulty honor of silence, use it too liberally and for gaining advantage.” (Perhaps this is why he is so fascinated by Kwang, the Korean American politician who functions so effectively, so openly and communicatively, in American society.) Henry finds a kind of peace at the novel's conclusion when he starts working with Lelia as a speech therapist for non-native speaker children. He watches the children discover the fun and flexibility of language—something he wishes he had been taught when he was acquiring his second language in a country where language and its politics can so easily sway perceptions of identity. As the kids see Henry as a model of success (someone whose "voice moves in time with his mouth, truly belonging to his face" as he owns the language), he comes to an understanding about what it means to be a "speaker" and a "native" (eNotes). It's hard to draw definitive conclusions about what it means to be a male Korean American—but Henry at least seems to have made peace with one aspect of it as he reconciles with his wife and breaks the "silence" he has held onto in his personal life (and rejects his previous public one when he quits his job).
I also think there's a lot readers might learn about America. One of the most salient details to me seems to be the way Park questions whether one can be a "native speaker" and still hold onto one's cultural heritage in the US today—and whether even then the country will recognize an Asian face as truly "American." The novel also suggests a deep reluctance in American politics to accept recent immigrants as candidates (as illustrated by John Kwang's fate). It also draws a vivid portrait of the way immigrants are made to fight or betray each other (as Henry betrays John, who has trusted him in part because of their Korean connection). Henry is so aware of the linguistic and cultural legitimacy denied to those with Asian faces that he chose to raise his child without Korean customs so that he would have "the authority and confidence" that Henry himself never felt.