content: I believe we had some great unity especially after 9/11.  Well sure, we were united ...against terrorists. That's the only way to make such unity happen. Homo sapiens are a tribal ape, and a tribe only has meaning as a delineation between it and some outside group. You can have a tribe of Americans so long as there's another tribe called "terrorists" for you to fight against. Absent that, you can't have the "Americans" tribe, because without someone to fight, the tribe has no meaning. We form tribes instinctively. It's a deep-seated need. We form them around sports teams, nations, races, whatever we can think of, but there has to be someone to fight, otherwise we're not meeting our instinctive need. If Earth were to be invaded by aliens, then you would see humans united, because we all would have something to fight. But since that's not going to happen, humans will never (not unless this instinct is lost) be united.