Both Japan and Israel are expansionist (culturally, economically, politically, and at varied times, militarily too), and this makes for a world of difference. I guess I muddled things when I said Isolationist when I meant Extreme Isolationist (both xenophobic and anti-expansionist).
Singapur, Honkong etc. are not independent and act under an umbrella of a larger state.
The real world example of such utopia would be arguably the Aztec, the Maias, or the urban native civilizations in North America. However, irl this doesn't happen as often, since idealized examples like Wakanda do not exist.
And of course, the smaller the utopia is, the sooner it will meet its end.
@Martin:
No, that is not what Aryan is. Aryan is the most accurately named Indoeuropean, and shares a heritage of a common land of origin, namely steppes north of Causassus, in the land called Scythia or Sarmatia. This does include Persians and to some degree, Indians (although their blood got mixed with numerous indigenous inhabitants of the Indian Peninusula, while Europe was likely more or less empty when Indoeuropeans arrived).