I wouldn't interpret it quite that way.
Cultural changes occur over time, as they do in any society/culture when interactions with external influences take place (the influences could be another faith or different cultural practices of foreigners etc.), and overtime the culture changes from what it was originally. This is nothing abnormal, and the change in cultures that convert to Islam is to be accepted as part of societal evolution.
The issue in the subcontinent was that you continued to have a second even larger culture (Hinduism) exist side by side, and some in the second culture (to me) seem to have continued to view the Islamic culture as being under its umbrella, whereas over hundreds of years the Islamic culture grew to view itself as separate.
I believe this is a process that occurs everywhere. The human race started of as one after all - then you had divisions on family lines, Tribal lines, Racial lines, Cultural lines ---nationalism.
The Muslims making up Pakistan did the same thing. Its just that the way history played out in the sub-continent makes the situation more acrimonious than it should.