Jack, yes, WWIII would qualify as the worldwide catastrophe of which I speak. I never said everybody would sit around singing campfire songs and say, "Okay, heck with this...let's all just get along and be nice." I said a (pick your favorite) CATASTROPHE. Surely we all agree it's a race to see which one happens first. And I'm NOT an alarmist. True, some technological miracle(s) might come along to save us from ourselves. That's a definite possibility(ties)--i.e., nuclear fusion, for instance. Aliens may intervene. Jesus might FINALLY come back (that was a joke). But by my way of thinking, a World Government, possibly preceded by a confederation, maybe totalitarian or fascist to begin with or devolving into that or EVOLVING into something truly advanced, whatever, but one way or another, it's coming. Agree? Disagree. It's inevitable.

IMO - the biggest problem with us ever having a whole-world Government is that people are almost universally tribal in their nature. Even those of us who try to be aware of diversity and other cultures do it to one extent or another. We always - even if only in subtle ways - subdivide ourselves into 'us' and 'them' camps. It would take something like a 'First Contact' episode from Star Trek to get us to view most of humanity's diversity as the bigger 'us'.

And as Bobby9 (the most recent previous comment as I type this) wrote, a single world Government couldn't possibly effectively represent the aspects and needs of more local populations.

Theoretically speaking I would totally agree. But how to put that into operation short of a 3rd WW. And once in place how t=will it work. If bureaucracy is so bad at a national level imagine what it would be at a global level?

is

A machine government and a complete reconstruction of human social systems, voluntarily.

There are no humans capable of not being corrupted. Human govt will always be fallible. Human govts lead to totalitarianism.

"Is not what your country can do for you....."

Capitalism is not capitalism without competition. People need to understand that. Everyone is angry at Facebook but we are now a nation of "goods and services." Find something in that area and you might become rich. If I browse anything anywhere I go on Face book 10 minutes later and they are showing it to me in ads.

I do not feel a government located a jillion miles away can properly assist my needs...in fact, that is IMO one of the problems in this large country, the problems of a small cattle rancher in Arizona have Nothing to do with us here in New England! i would like body governing interactions between countries, like a powerful UN maybe, but local "fiefdoms" to respond go my day-to-day concerns.

A loose confederation with limited power over local governments and small costs (basically elected UN with some real power and a small peacekeeping army and investment budget).
The problem of a world government is the shape and culture. The world changes governments must adapt.
Europe, South America and Africa (EU, Mercosul and AU) are trying to create this large confederations. But is difficult to create a huge state that will keep its democratic ways for everyone.
Imagine that in a world govern elected, the high executuve power would alway probably be in the hands of a Chinese or Indian politician.

True it could be a good thing, but I do not think that any worldwide catastrophe would ever be great enough to persuade the oligarchs to pull together before it became so great that it pushed the world into total anarchy. And secondly any global government would, by dint of human nature, immediately split into the orthodox and reform groups, possibly destroying the UN, and from which conflict even a global conflict on the ground could follow. I think that it is more likely that governments and the UN will be forced into reform by global democratic pressure from below, if things like the internet produce a global consensus among the greater numbers of people, but I do not hold out much hope for that either.