I see nationalism as a phenomenon no different from a bunch of ppl forming a grp in the class durin schooldays. Its human nature, to form grps and societies. A nation is just a larger form of the same. Man being a social animal needs a society, a community and at a larger level a nation to survive.(jus to survive). An organised human existence is hard to imagine without the existence of nations. An important factor here is the basic desire in man to gain a superior position than others. Individually this would hav been difficult. So nationalism, which i believe comes instinctively to us was the only solution.
Also i believe its not only the culture that leads to formation of a nation. Not at all. 59 yrs back the cultural diffrences between Delhi and Lahore were far greater than those between Delhi and chennai. In fact this may be the case even today. Still Delhi and Chennai find themselves in the same nation and that too a successful one if i may say so. So there are a lot of factors which lead to the formation of a nation which actually me and you as a single person can not analyse so easily.
All that we can do is appreciate the fact that the phenomenon of nationalism is afterall for good.
And yes we do take a lot from what we call our our country and a social debt does exist for us to pay.
So i wouls suggest: just take pride in being a part of whatever nation you belong to. Believe it or not your nation does have a great impact on what you are. So celebrate the unity of a grp of people who did nothin but had a synergy amongst them to mutually coexist and co-develop. Thats what nationalism is for me and thats why i m proud to be an indian.