If we can get to the stars after unifying then we would be pretty safe from ourselves. That would mean we have evolved enough over time to realizing kicking the stuff out of each other wouldn't get us anywhere, creating peace. I would worry more about what is out there, alien races that might've made it to space but are either xenophobic or extremely hostile, something that would attack us. Fighting an alien race that has been around for god knows how long would be like the Conquistadors fighting the Aztecs, we would be the Aztecs and we would stand no chance.