Am not sure how far that 'dharma' goes...to this day, a south indian travelling through interior northern territory for example is not that different from a westerner in India..in terms of appearance, language, everything - and cities are not the barometer we judge the country by, it is how you are treated in real interior country. I have met many 'indians' here in the west for example...citi bred educated lot are different but people coming from rural areas do regard fellow indians from other parts of the country, as total strangers.Wonder how other people's experiences are in this regard - to my mind the 'dharma' is a fragile concept when it comes to practical realities and perhaps help you stick together when faced with a non indian but not otherwise.
Our existence can be sliced and diced in variety of layers. You are picking up layers where there are differences. As one goes up the layer (think abstraction), there is a whole lot more common about us. There is a lot common between a tamilian anda bihari than say a bihari and chinese. One can find differences - I am not saying they don't exist. Similarly one can fight lots of commonalities between a Punjabi and Andhrite.
'Dharma' is a very complex topic, and it is one of the greatest things India has given out to this World. I am not sure what you mean by it being 'fragile'!
Dharma as a personal concept is a lofty great thing, or even within people who acknowledge one another as community. The problem with presesnt day india is a clear lack of community among people drawn from different parts...dharma or any other philosophy is not practiacl enough to create kinship among say a guy from UP and a guy from Trichy and treat one another as brothers..they are as strangers to one anotehr as an american and an indian who meet first.. and i dont mean elite city folk just those drawn from smaller towns and villages..we may rave about dharma in the practical world there is no kinship created like that that is all.