How did the punic wars lead to the fall of the roman empire

They didn’t. The Punic Wars, fought in the second and third centuries BCE, were between Carthage and the Roman Republic. The empire began over a hundred years after the end of the third and last Punic War (149-146 BCE). The fall of the Roman Empire (in the West, anyway), occurred almost 500 years after its founding (27 BCE), by which time Carthage had been destroyed, rebuilt, made part of the Roman empire and abandoned to the Vandals.