Both Ashoke and Ashima come of age in the aftermath of the Partition of 1947, when India and Pakistan were granted independence by the British government at the same time that they were also separated into two distinct nations. Ashoke and Ashima are from Calcutta (now officially spelled Kolkata), the capital city of the Indian state of Bengal, which borders Bangladesh. When Ashoke's train gets into an accident in 1961, the novel tells us that the accident may have been the result of sabotage, presumably from terrorist organizations working within Bengal at the time.
The novel doesn't really get into this history, though. In fact, we don't learn much about India at all, since most of the story is told through Gogol's eyes, and Gogol spends most of his time in Calcutta cooped up in one relative's house or another.
But this might be a good time to learn a little something about the term Bengali. We know that the Gangulis are from India, so why don't they just refer to themselves as Indians? What does Bengali mean, anyway?
Bengal is a region in South Asia, now divided between an eastern portion of India, and the country of Bangladesh. Bengali people, like the Gangulis, are simply people who are from this region. More specifically, the Gangulis are from Calcutta, which is the biggest city in the Indian state of West Bengal.
So when the book talks about Bengali traditions, Bengali language, and Bengali people, just remember that they're from Bengal. India is a huge country, and Bengal is just one part of it. And when The Namesake refers to Bengalis, it's being more specific that using the term Indian. Lahiri is being truer to her character's roots.
Gogol's parents arrive in the United States in 1968, part of a surge of Asian immigration that began in 1965 when the United States abolished its national origin quotas (rules stating that only a certain number of immigrants were allowed from a given country). As one of the first children born during this wave, Gogol is also the oldest of his family friends' children. His younger sister Sonia has more Bengali-American friends her age than Gogol does. Important historical events such as the assassination of John F. Kennedy, the Vietnam War, and Ronald Reagan's presidency are mentioned in passing, but these don't seem to have a profound impact on the characters.
The characters bounce around from Boston to the suburbs to New Haven, to New York, to Ohio to New Hampshire to New Jersey. But what's important here aren't the places and names. It's the cultural environment that counts. Gogol and Sonia in particular feel the enticing pull of American culture, convincing their traditional parents to "celebrate, with progressively increasing fanfare, the birth of Christ, an event the children look forward to far more than the worship of Durga and Saraswati" (3.59), and leaning towards Caucasian romantic partners as they grow older.
Their cookie-cutter Boston suburb couldn't be more different from Calcutta, and it's this contrast that helps us understand the two conflicting sides of Gogol's identity. Perhaps Ashima has the right idea in the end; the only way to deal with these two starkly different places is to split your time between the two. Allow yourself to be both American and Indian, all at once.
The other region that plays a part in the novel is Moushumi's Europe. She was born in England, and spends a big chunk of time in Paris as an adult. She and Gogol later revisit Paris when she attends a conference there. Plus, the pair plans a trip to Venice, which Gogol takes alone, after the divorce. The scenes in Paris and Venice emphasize how foreign these cities are to Gogol, who is used to shuttling between Indian and American cultures. They also serve as a subtle reminder of the European origins of Gogol's first name.