Editing VDARE.COM, I spend a lot of time taking the word "nation" out of writers' copy. What they mean is what in British English would be called a "state". But as I wrote in Alien Nation:

American editors are convinced that the term "state" will confuse their readers unless reserved exclusively for the component parts of the United States–New York, California, etc. So when talking about sovereign political structures, where the British would use "state," the Germans "staat" and the French "I'etat," journalists here are compelled to use the word "nation."

Thus in the late 1980s it was common to see press references to "the nation of Yugoslavia." Of course, Yugoslavia's problem was precisely that it was not a nation at all, but a state that contained several different small but fierce nations–Croatia, Serbia, etc.

(In my helpful way, I've been trying to introduce, as an alternative to "state," the word "polity"–defined by Webster as "a politically organized unit." But it's quite hopeless. Editors always confuse it with "pohcy." I've also tried "country," which is sometimes an alternative in British English. No good either. They seem to think that's a type of music.)

This semantic weakness really impairs American debate on immigration, I argued:

RESULT: Americans who confuse basic terms in this way must inevitably also get confused about what a nation-state is, what its function is, and what it requires in order to survive.

And I supplied a defintion:

What is a "nation-state"? It is the political expression of a nation. And what is a "nation"? It is an ethnocultural community–an interlacing of ethnicity and culture. Invariably, it speaks one language.
In recent years in the United States, there has been a tendency to emphasize the cultural part of the equation. But this is to miss a critical point. The word "nation" is derived from the Latin nescare, to be born. It intrinsically implies a link by blood.

Of course, if a nation-state has an ethnic component, mass non-traditional immigration becomes much more problematic.

As it happens, the geopolitical intelligence publisher Stratfor has just posted a powerful essay by Dr. George Friedman, 2008 and the Return of the Nation-State, arguing that both NATO's confused reaction to Russia's invasion of Georgia and the world's reaction to this fall's financial meltdown show that in crises individual nation-states, and not multilateral institutions, are what count: "The nation-state was the only institution that worked."

Friedman's definition:

A nation is a collection of people who share an ethnicity. A state is the entity that rules a piece of land. A nation-state – the foundation of the modern international order – is what is formed when the nation and state overlap.

Friedman's conclusion:

The world is a very different place from what it was in the spring of 2008. Or, to be more precise, it is a much more traditional place than many thought. It is a world of nations pursuing their own interests and collaborating where they choose. Those interests are economic, political and military, and they are part of a single fabric. The illusion of multilateralism was not put to rest – it will never die – but it was certainly put to bed. It is a world we can readily recognize from history.

Immigration enthusiasm will never die either. But in what Friedman calls "a world of nations", it has only a limited future.