Much of the narrative is set in the Kuru-Panchala realm, and nearby kingdoms - Madra, Virata
What's anomalous are kingdoms far, far away from this "core" zone -
Yadavas of Dwaraka (who relocated from Mathura)
Magadha (Jarasandha)
From a historical standpoint, the "core" geography of the middle-Vedic period is in the region around Haryana, West UP (maybe east Punjab)
But later tradition appears to incorporate v far off kingdoms like Anartas, Magadha in the core epic narrative
But were incorporated in a later period (post Buddha) by which time Aryan culture had spread far beyond the core "brahmavarta" region?