Saying "Nubian" is so much easier, though, Sumskilz. It's easier than saying "the Kerma culture of Bronze Age Sudan that was conquered by New Kingdom Egypt, Egyptianized, and morphed into the Kushites centered at Napata and Meroe that briefly conquered Egypt under the 25th dynasty". Doesn't roll of the tongue or fit into a single Tweet quite like the one word phrasing, Nubians.
The Punic Wars are a great example of why the Romans decided to settle on expansionism, because the threat of Carthage was too great and they couldn't avoid the risk of being a second-rate power to it. Perhaps the First Punic War could have been avoided, but the Second Punic War was arguably unavoidable. Once Hannibal secured Iberia, whether Rome decided to declare war or not, Hannibal was gunning for the Romans since childhood with the stories passed down by his father. He would have most likely invaded Italy anyway, or provoked the Romans to declare war in another way, by attacking their allies in southern Gaul, such as the Greek colony of Massalia.
Excellent points have already been made, though, about why Rome was different under the First and Second Triumvirates of the 1st century BC, as opposed to the earlier phases of the Roman Republic that saw more gradual expansion due to reactions to immediate crises. If you think about it, Rome really only got involved reluctantly in Greece because Philip V of Macedon had the bright idea to directly ally with Hannibal of Carthage. Rome had previously been attacked by Pyrrhos of Epeiros just decades before this, so the threat of a Greek power conquering Magna Graecia in southern Italy wasn't some "pie in the sky" idea. They viewed Philip as a legitimate threat, not just something across the Adriatic Sea that they never had to worry about.
In the case of Cleopatra VII, she was very unique in that she was basically the only client ruler of the Republican period to possess so much clout within the Roman system. Had she ultimately succeeded, her children would have been monarchs of large Roman client kingdoms throughout West Asia, Cyprus and Libya, and their Roman parentage would have ensured their safety more or less. However, the reason why so many soldiers and officers even before the Battle of Actium started to desert Antony and flock to Octavian's side was because of the rather unpopular moves by Antony to carve up the Roman east in this way, cementing a personal and indirect rule over the eastern part of the Roman world through his royal children. Octavian ultimately won over the Romans not just by having Agrippa win the battles, but by dressing up his arguments in a comforting republican facade.