It's possible you're thinking of a different animal or a different state. Some species have been intentionally introduced to new areas to control other populations, but it's not a common practice in the case of porcupines.
What animal was brought into pa to kill off porcupines?
There is no documented instance of an animal being brought into Pennsylvania specifically to kill off porcupines. Porcupines are a native species to Pennsylvania and are not considered an invasive or overly problematic species.