First of all, thank you for your reply and mad respect for all your knowledge and posts in this thread. It's great to see somebody with your passion and interest in ancient history.
I'm actually writing an Honour's thesis right now on the growth of Roman imperialism during the period 280 - 168 BCE, and the Second Punic War plays a key role in my study. My interpretation of it is that the source of Roman power did not lie in the militaristic attitudes and culture of Roman society and politics; rather, the true source of Roman power laid in their alliance system and their ability to get their allies to deliver on their military commitments year after year. Even for those scholars who argue that it was a manpower advantage that allowed the Romans to constantly lose battles but always win wars, they overlook the importance of the alliance system. During the mid-Republican period, all Roman armies were comprised 50% of allied infantry and 66% of allied cavalry; overall, less than half of a Roman army was actually Roman. The rest were Italians to begin with, and later on, Greeks, Numidians, Gauls, Iberians and so on. So as far as Rome's manpower advantage goes, the only advantage was that less than half of their armies were made up of Roman citizens, whereas most other states fielded a combination of their own citizens and mercenaries. From the 86,400 they brought to Cannae, 40,000 infantry and 4,000 cavalry were Italian allies, against 40,000 infantry and 2,400 cavalry who were Roman.
In the example of the Second Punic War, we can see that Rome's enemies perceived the importance of their alliance system to the power of the state, hence Hannibal focused his campaign strategy on breaking the alliance system through sparing and freeing allied soldiers in Roman armies but executing and capturing all Romans. He knew that the Italians were only in bed with the Romans because they had no choice in the matter, and would surely abandon their alliance when they saw somebody who could defeat them come around. When Varro, the surviving consul from the defeat at Cannae, spoke to envoys from Capua after the battle, he was on some "thank God you're here to save me" type shyt. When the envoys returned home, the Capuans decided "we better go over to Hannibal," perceiving the weakness of Rome at that moment. And his eventual defeat at Zama was because Scipio was able to get the Numidian king to break his alliance with Carthage and come over to his side, which gave the Romans access to the same Numidian cavalry Hannibal had wrecked them with throughout the war.