The difference is that no one clan in India comprises any majority. Again, imagine a country where the french lived next to the english and the italian (like literal next door neighbors), but kept their own languages, customs, etc and only intermarried people like them. That is India. There is ample evidence for this. The differences between the cultures can be extreme.
It is relatively recently that any person in India would even claim to be 'Indian'. Most identify with the state / jati they belong to. Yes, they're 'Indian' in the same way that an Indian is 'Asian' or an Englishman is 'Eurasian', but it's not a coherent identity.
The indian gov't is certainly trying to make that a reality (this is the source of their 'Hindu nationalism' -- which is really a particular kind of North Indian hegemony), but it's been a long time coming, and there are a lot of issues with it.
Since when does a country mean a single cultural group? By that metric Switzerland, Russia, the UK, Belgium, France, Italy, Spain, Central Asia, most of SE Asia, any country in Africa, large parts of the Middle East and South America are not countries. For that matter, all of China isn’t Han Chinese, there are Tibetans, Mongolians, Uyghurs, Zhuang, Hui etc.