I have heard that Hannibal was unable to because of his lack of troops, though I believe that, after the many maneuevers he had been able to pull off in the previous years, he would have been able to capture Rome and possibly put an end to the Republic in it's infancy.
Also, what was the impact of Macedon against Rome since it sided with Carthage in the second war, I believe. Did they play a big role or were they just a sideline?
I am dubious of that claim. Firstly Hannibal's army, despite their stunning success at Cannae, still had suffered significant casualties and needed a few days to recover. Furthermore I'm not aware of any references to Hannibal bringing along a siege train and the lack of one would make any siege of Rome incredibly difficult. Rome was protected by the Servian Walls so taking the city would require a long and costly siege surrounded by Roman allies who could muster another army and catch Hannibal between a relieving force and a sally from Rome. Lastly how many of Hannibal's men would have the skills for siege work?