In fact, many argue that modern globalization is better suited to smaller forms of government than the XVIII century typical Nation-State on the French model. The concept of "Europe of Cities", on the model of federal Germany, is actually pretty compelling: most citizens of, say, London, have more in common with the citizens of Milan or Prague than they share with home-county backwaters; and the instances of the British countryside are closer to the ones of French countryside than of post-industrial cities like Manchester. Having London-sized macro-regions meet at European level to coordinate might be more effective and representative than the current "deep" model. It would also neutralize a whole set of issues with regional "independence" movements: Catalunya, Scotland or the Milan hinterland would be peers in Europe, rather than subjects in Milan, London and Rome.

Historically, nation-states have been mostly defined by culture, which is defined by language, which was mostly defined by communication speed, which was mostly defined by actual transportation speed. That's not an element anymore because all culture can be everywhere at any time. A new approach is required.

City-states have historically lead to far more numerous wars.

I won't argue the fact that Cyrus was enormously influential to the course of fertile crescent civilizations. That said, really he was just one of the first Fertile Crescent leaders to see not only the weaknesses of the city-state, but the means by which to exploit those weaknesses. (It's just that what he did to exploit those weaknesses was so radically orthogonal to the way things were done at the time that even today we're still calling the guy Cyrus the Great.)

Once the Nation-State idea was out of the bag, city-states just couldn't compete. Even the Greek city states fell to Macedon because by the end of the Theban hegemony, they were all so weak that even Macedon, effectively a baby nation-state at the time, was able to take them out. City-states wouldn't be able to compete today either. You'd always have to have some great power around to back them. Even Federations of city-states have faired poorly historically.

It's like continuing to rely on bronze swords once people got the hang of making iron ones. It no longer mattered all of the reasons that bronze was better for you, because iron was better when it counted. The cat was out of the bag, you could try to put it back in the bag, but everyone's already seen it.

All things come with problems. Lots of small principalities may have better local goverance, but they tend to squabble.

The other thing is that a place like Singapore is exceptional. It’s a strategic chokepoont established by a colonial power.

Welcome to feudalism.

> This sounds like an argument for smaller nations?

It is sometimes used as one, thought it is also sometimes argued that the advantages of city-states are offset by problems (among others, international instability) unless the city-states are relatively rare and economically engaged with (and buffered from each other by) larger polities.

India has a similar situation. All the south Indian states are demanding to be declared as separate nation. One of the Singapore's official language is Tamil whose origin is an south Indian state TamilNadu. Singapore is taken as a motivation to demand a separate nation.