Carthage was Rome's main rival in the third century BCE. The Carthaginians were able merchants, wealthy, well-connected, knowledgeable, and they had a strong land and sea military. Definitely trouble for Rome, and not that far away.
When Rome defeated Carthage in the Second Punic War, it cleared the way for Rome to dominate the trade of the western Mediterranean. And since the Greek states seemed intent on destroying each other (and Athens itself from within), this really allowed Rome a safe neighborhood in which to become dominant.