You appear to be using as your definition of country "member of the UN." If you want a canonical list of countries, that's about all you can do. But I don't trust authority to list countries just as I don't trust authority to list poisons.

We differ on that point, then. The concept of "country" as I intend it here is more or less entirely a matter of what authorities list (in contrast to the concept of "poison", which involves the question of whether something kills you). The authorities here aren't epistemic ones pointing to empirical facts, but are rather political ones making declarations that they intend to enforce.

"Member of the UN" is at least a sufficient condition for countryhood, and the sense of my original comment is approximately the same as if it read:

You're talking about Dubai in a way that suggests you might be under the impression that it's a member of the UN. But it's not; instead, it's part of a member called the UAE.