Please brush up your history. India came from 'Hind', which the Europeans couldnt pronounce. 'Hind' in turn came from 'Sindhu', as in the river, which the Greeks couldnt pronounce. India has as such never been a separate entity not just for Britishers, but for any outsider, Persians, Greeks, Central Asians like Babur (Mughal founder) etc. For eg. 1. Alexander didnt win just the land of Punjab, he said I won against India. 2. Vasco -da-gama never came to 'Kerala'. He went to the coast of India. 3. When Britishers came and first camped in Calcutta, it wasnt 'Bengal' that they landed in. They called it India & named their country the East India Company.
However, it is true that the local cultures of various states are coming under pressure from Bihar & UP because of their poor moving into other states because of bad governance in their own states. With them overflowing into prosperous states, overflow the drainage systems, toilets, defecating in the open. They also bring with them the ethics that they learnt there, which arent much, spitting, loud behavior, an accent which sounds rude (even though what they are saying may not be rude).
Hence the backlash in Assam, Maharashtra & there is resentment in Punjab because of it. Delhi's governor & CM dont like them either & have said so. It is true then that the present generation needs a new consitution.