I do not think a `world government' is possible; it may not be desirable. But governments covering larger territories are possible now, but only if they provide several sources of power.
But first why the notion of `world government' is dead.
Two generations ago, `good government' people (`goo-goos' they were called by their enemies), liberals of all kinds, and others, favored a `world government'.
They saw that the United States formed out of previously independent states. In Europe they saw previous enemies coming together to form a common market. By a parallel reasoning, they figured that the United States, the Union of Soviet Socialist Republics, France, and Egypt could all join together in a powerful and unified federation.
My father, I remember, told me that the different countries that sent diplomats to the United Nations were no more different than the original 13 colonies that came together to form the United States. The US had slave states in the south and free states in the north; it had politically powerful men who made their living on agriculture and it had men of commerce. His belief was that if the various parts of the US could come together voluntarily, then in the modern world, everyone could come together.
Moreover, he believed this could happen peacefully.
Nowadays, people think differently. First, few think the US or China, to take two examples, would both peacefully give up their sovereignty.
Secondly, I have not recently heard either modern US Liberals or Democrats favor a world government. Certainly, none have said that they favor a world government under a politician such as George W. Bush.
Indeed, a good many Liberals and Democrats in the US argue that the US should not conduct wars abroad, and that the current US war in Iraq is a mistake.
If implemented, this policy would prevent the US from taking part in military operations designed to make a `Federated World Government' an effective government rather than a pretend government. It means that the US could go no further than support a permanent diplomatic conference, a `talking shop'.
At the moment, as far as I can see, the only people in the US arguing for governmentally-funded coercive action on a world-wide scale are people on the political right. They are dismissive of non-US influence, which is to say, they are against a new government that reduces US power.
Consequently, both the current US administration and its domestic opposition are against a world government.
That tends to kill the notion.
But a different proposal pops up: not a world government, but a `coalition of the willing' or a `union of democratic states'. The idea here is to replicate the experiences of the US and the EU in their founding. The goal is to bring together countries that want to join each other, and are willing to surrender some of their sovereignty in the process.
I do not think that people in the current US Bush Administration envisage a new organization that would reduce US sovereignty. They speak of acting unilaterally. But other US Republicans might figure a new form of government would help them.
(Some of these people, like James Webb, President Reagan's Secretary of the Navy, have referred to the US invasion of Iraq as "the greatest strategic blunder in modern memory." Others are fearful of the Bush Administration's deficits. Even when deficits profit them in the short term, they look at Federal government deficits that are projected to extend forever, and fear that the country will become weak in a generation or two. They may figure that they should embrace an organization that might help them in the long run.)
In any event, let us consider how to put together a `federation of the interested'. (I think the European Union should consider this, too, just for itself.)
As far as I can see, we need a three chamber legislature, not a one or two chamber legislature, as is now common. Power in the third chamber would be based on actually paid taxes, not on history or on population, the two current mechanisms.
This is a cynical proposal. However, it has the advantage of convincing rich countries that they will not be overwhelmed by poor but populous countries or by a coalition of small countries.
If the US joined such a new country, this proposal means that the US would continue to have great power ... but only so long as it continues richer than others and so long as it pays its taxes.
Poor but hopeful countries could hope that they would gain power without war. Such countries fear a repetition of World War I, which many think occurred because Great Britain, France, and Russia were not willing to give peacefully some of their power to newcomer Germany.
Another chamber should be based on population, like the US House of Representatives. This looks to me like a good way to help ensure justice.
A third chamber should be based on history. That is to say, it should be based on the principle of one (or two) votes per nation-state, as in the current UN. This is similar to the arrangement for a Senate made among differently sized states in the US at the time of the framing of the US Constitution. This attracts small countries who otherwise fear they maybe overwhelmed by the large.
(Some contemporary countries are very small. Consequently, the disproportion in power between large ones and small nation-states is even greater than it was in the 1780s between large and small US states. To prevent this disproportion from wrecking the whole proposal, it may be necessary that some small countries federate with each other.)
As for the chamber in which power is based on taxes paid:
Another issue is called "veto power" in the UN and "states' rights" in the United States.
In the UN, certain states can veto mandatory Chapter VII resolutions (These are different from the more common, non-mandatory Chapter VI resolutions. The permanent members of the UN Security Council can also veto Chapter VI resolutions, but since they are voluntary, and give no nation a legal right to enforce them by war, they are less important. The US based its legal right to invade Iraq on mandatory Chapter VII resolutions.)
Clearly, the United States will not join an organization in which it cannot veto actions that the government of the US believes will damage the US.
Consequently, some sort of veto is needed. But the question is what sort? The United States itself was founded with vetoes of a sort. These are called "states' rights" and they hinder a Federal or `super-state' government from taking actions that individual states dislike.
In the US between 1790 and 1990, the constitutional provision of states' rights was moderately successful: that is to say, the US suffered a civil war in the 1860s, and after 1950, states' rights eroded peacefully.
In contrast, western Europe lacked the notion of "states' rights". Between 1790 and 1990, Europe suffered the Napoleonic Wars, the Franco-Prussian War, World War I and World War II.
Even though "states' rights" were not completely successful, they helped; over the 200 years from 1790 to 1990, the US suffered fewer internal wars than western Europe.
Consequently, some measure of "states' rights" look necessary. I do not know what they should be.
(I suspect that the time period considered salient for this issue by US decision makers will be two or three generations, even if their salient time periods for other decisions are only two or three months. Hence, this issue will be important.)
Incidentally, "states' rights" are similar to "individual rights", such as the right to free speech. Individual rights hinder a government from taking actions that individuals dislike. Both the US and the EU have codes of "individual rights", as do other countries. Another issue is how well these codes are followed.
A few details about a three chamber legislature:
It will be hard to build agreement in a three chamber legislature. Much will not happen. Some argue that in government, this kind of `grid lock' is no good. Others argue that you can ensure a more or less peaceful form a domestic dispute resolution only by patiently persuading enough people and powers.
Peaceful dispute resolution is the first goal of government. That goes without saying. A second goal is justice. Currently, some international disputes are settled peacefully through the World Trade Organization and similar organizations. (At least they will be settled peacefully so long as the members figure they are better off losing gracefully than destroying the process.) But the WTO and its ilk not only lack military power, they lack the legitimacy provided by the mechanisms of a representative government. That is why the EU invented the European Parliament. While that legislature lacks much power, it is felt to be better than nothing.
The goals of a three chamber government would not only be to bring peaceful international dispute resolution into the realm of the domestic, but also to bring some degree of legitimacy to such action.