Funny, because Eastern India was pretty much the nucleus of Indian civilization for a LONG time. That includes "retarded" Bihar. Cultural elements were pulsing out of Bihar area into other parts of India, then from India to SE Asia, etc.
Even if we agree Maurya was from Paliputra, wrong but lets agree. Pakistan either had indigenous empires or invaded from west, a part from two ocasions. Gupta Empire and Maurya for just mere 300 years combined. And Maurya ancestry is questionable anyway but Chanakya was born in Pakistan.
Eastern India was hindu ganga civilization, its distinct from Dravidian civilization of South. And hardly had impact on Pakistan a part from 300 years thousands of years ago.