In Pakistan, regionalism is a product of the independence movement itself. When the Muslim League launched its final movement in the 1940 for a Muslim homeland in the Muslim majority provinces in the North-East and North-West India, the Punjab and Khyber Pakhtunkhwa were ruled by anti-Muslim League governments, while Muslim League’s position in Bengal and Sindh was also weak. Therefore, central government of Pakistan distrusted
the provincial leadership completely. While Punjab was increasingly identified with the Centre, the other provinces felt betrayed and their intelligentsia duly represented this dissatisfaction with the state system of Pakistan.
Being inherent in a multi-national country, regionalism as such is not a problem. What makes it problematic is it steady growth & eventual influence over centripetal forces upsetting federal-state equation.