With many of the questions that you have been asking, there has been a clear answer given at a specific place in Traditions & Encounters. With this question, by contrast, there is no specific place where Bentley and Ziegler explicitly tell us how India was affected by its lack of political unification. Instead, we have to infer the answer from various parts of the chapter.
The main thing that we can say is that the lack of political unity after the fall of the Gupta Empire weakened India and made it more susceptible to pressure from the outside. This may well have helped to allow outside influences to become part of Indian society. Because India was divided politically, the rulers of its various states were not able to join together to fight effectively against invaders. This led to invasions such as those of the Central Asian people who came to India through Afghanistan.
These invasions changed India’s political landscape. They also changed Indian culture. Most importantly, they helped to bring Islam into India. This changed Indian culture as many Indians converted to Islam and others adopted aspects of that faith.
Thus, we can say that India’s lack of political unification affected it both politically and culturally since it allowed outside forces to enter India and gain political and cultural power.