Matthew Yglesias has a post about Will Marshall's idea for a Global NATO.
I think that, eventually, there will be something like a Global NATO. But not for a long, long, time. You see, history (from my perspective) is the slow unification of small, atomized societies (even as the individuals within those societies seem more atomized because of how large the society they live in is--does that make sense? The whole gets larger but the individual gets more diluted? Eventually, I think, we're going to have a very, very loose global government with a more effective system than the current Global Government (the UN).
But what do we do in the meantime? Well, NATO and the EU are ahead of the game: they've unified Europe. But how did it happen? Well, by the end of the 20th Century, the member states of NATO and the EU had two things in common: very similar forms of government (comparatively; whatever differences in government there are between, say, Poland and Ireland, it pales in comparison to the difference between Communist China and England), and very aligned interests. At the end of the day, all of the states of NATO and the EU stand together or fall together.
Will Marshall seems to believe that we should take all of the countries that have interests aligned with the US/Europe, and put them into a Super-NATO. But the obvious interests we have aligned can't paper over the interests we don't have aligned. That isn't to mean that there are specific issues that Japan and the US butt heads on (no more or less than between France and Germany); it's that certain interests that are very important to Japan and South Korea are considered unimportant to countries like Poland and Italy. To a certain extent, it would be like California weighing in on certain issues that really only matter to New England.
A regionalized system, although imperfect (and in certain areas, doomed to failure) is the beginnings. It is part of the reason that the UN doesn't work.
Suppose NATO and the EU were to create a model for North America. The United States would start to take a greater interest in the way that drug gangs have caused chaos in Mexico; the resources of the NAFTA nations would be greater applied to create peace an stability. Then, say that the OAS bridges the gaps between Latin and South American countries. Suppose the AU slowly develops (over many, many years) into becoming an actual supra-government for Africa, bridging their interests, decreasing wars, increasing train. The Arab League creates a supra-government for the Arab member-states, bridging divisions between Syria, Egypt, Jordan, Saudi Arabia, etc. Maybe SEATO would, in a meaningful way, bring the nations of the South East Asia together.
Then we get six or seven region-blocs. Where they cooperate, they could work jointly. And whatever interests they share together, that would be the groundwork for a greater global government; rather than corralling the 192 countries into a global government (or letting five countries decide the fate of the world). The individual countries could also be represented (see: House of Representatives versus Senate).
That's my dream, but I'm warning you I don't see it happening in this half-century. The groundwork might be laid by the end of the century--Turkey and Israel joining the EU, the AU starting to come into its own, China somehow coming to a better relationship with its regional neighbors, NAFTA becoming a more genial organization.
But what I don't think will work is creating axises of opposing interests; some greater NATO linked only by their belief in Democratic Capitalism, and some hodge-podge of Chinese, Iranian, and Russian ally states (mostly rogue states and unstable states whose backers are the Chinese, the Iranians, or the Russians), and then a handful of completely isolated nations.