That's actually kind of the point of GP: the geographic limit here doesn't apply to the power of the sovereign around whose notional domain the line is drawn, it applies as a rule adopted governing relations between sovereigns but does not in practice apply where no sufficiently powerful sovereign has an interest at stake for which they will Lodge a protest (backed with the implicit threat of force.)
Parties using geographic games as a way to reject affiliation with recognized sovereigns are not evading the power of such sovereigns, only the protection of them.
Another key difference is that your phyle follows you around, geographically, while your nation's jurisdiction ends at its borders. If I'm an American expat interacting with another American expat in Shanghai, I'm still subject to Chinese law. If I'm a Neo-Victorian (to use one of the phyles from Diamond Age) interacting with another Neo-Victorian in Hong Kong, I'm subject to Neo-Victorian law. A block over could be a Han Chinese (also using the Diamond Age phyle, but in this case it corresponds to a real ethnicity in our world) enclave, and its citizens would be subject to Han Chinese law when interacting with other Han Chinese. If, as a Neo-Victorian, I cross the street to do a business deal with a Han Chinese, our dealings are governed by the Common Economic Protocol, the set of laws common to the federated system as a whole.
A nation-states jurisdiction does not end at it's borders unless it chooses for it to, which few do entirely. It ability to practically enforce it's rules may or may not do so, depending on the power of the state and power and interests of other states who may be concerned with the specific matter (especially, but not exclusively, the one in whose borders the target of the enforcement is located.)
It also was very pessimistic on technocratic solutions for the "good nurture" problem. Basically nothing can replace a real parent coaxing a self-expanding mind into beeing.
He's pretty good at imagining it too - The Diamond Age was published in 1995, just as the Internet was beginning to take off, and yet it envisioned The Internet, videoconferencing, smart paper, drones, and a whole bunch of other technological innovations that didn't catch on for 15 years or so. Cryptonomicon was published 10 years before Bitcoin but fully described two of its biggest use-cases, remittances and digital gold. Snow Crash had the "America is good at only 4 things: music, movies, microcode, and high-speed pizza delivery" line in 1992, 20 years before it became true and right as the rest of the country was celebrating us becoming the sole superpower.
I've never read anything else quite like it, and honestly don't know what I think of it. Are all of Neal Stephenson's books like that?
Note that "nation-state" has a particular meaning, and I think the word you're looking for here is just "state" or "sovereign state". Nation-states are sovereign states that are particularly culturally homogeneous.
> nation-state. noun. a sovereign state whose citizens or subjects are relatively homogeneous in factors such as language or common descent.
See: https://en.wikipedia.org/wiki/Mexican%E2%80%93American_War
and https://en.wikipedia.org/wiki/War_of_1812
The British even did heavy damage to Washington DC in 1814, including the Capitol and the White House: https://en.wikipedia.org/wiki/Burning_of_Washington
For example, California's "sanctuary state" law is a formal rejection of federal sovereignty over immigration. A full rejection of federal sovereignty would be secession, which we will probably see, at least de facto, within a century if trends continue as they are.
It is not, since they do not attempt to prevent the federal government from enforcing federal immigration laws in California. They refuse to assist such enforcement in any way - but that is a right that was always implicit in the federal structure of the government, and was made explicit by the courts in Printz v. United States (ironically, it was a 5-4 case split along ideological lines, with the liberal minority arguing in favor of the federal government able to commandeer state law enforcement).
If you want to see an example of actual formal rejection of federal sovereignty, that would be something like the Kansas' Second Amendment Protection Act, which explicitly declares:
"It is unlawful for any official, agent or employee of the government of the United States, or employee of a corporation providing services to the government of the United States to enforce or attempt to enforce any act, law, treaty, order, rule or regulation of the government of the United States upon a firearm, a firearm accessory, or ammunition that is owned or manufactured commercially or privately in the state of Kansas and that remains within the borders of Kansas."
A historical example would be the states' resistance to the fugitive slave laws. For example, here's Pennsylvania specifically targeting slave hunters in 1826:
"If any person or persons shall, from and after the passing of this act, by force and violence, take and carry away, or cause to be taken or carried away, and shall, by fraud or false pretense, seduce, or cause to be seduced, or shall attempt so to take, carry away or seduce, any negro or mulatto, from any part or parts of this commonwealth, to any other place or places whatsoever, out of this commonwealth, with a design and intention of selling and disposing of, or of causing to be sold, or of keeping and detaining, or of causing to be kept and detained, such negro or mulatto, as a slave or servant for life, or for any term whatsoever, every such person or persons, his or their aiders or abettors, shall on conviction thereof, in any court of this commonwealth having competent jurisdiction, be deemed guilty of a felony."
That part of the law was stuck down as unconstitutional. But the very same SCOTUS decision - Prigg v. Pennsylvania - also mentioned that the state could ban its officials and law enforcement from assisting in any way, and that's exactly what Pennsylvania did afterwards.
No, it is not; it is a (Constitutional, per cases dating back to the federal fugitive slave laws) refusal to expend State resources assisting federal enforcement of federal law. Leaving enforcement of federal laws to the feds is not rejecting federal authority or sovereignty.