This is stuff that, unless you've been living under a rock for 20+ years, everyone should know about. All of the "big" countries (both literally and in the news) are here, as are the major organizations.

More-or-less continuing from Layer 1, introducing entities that no longer exist as well as sub-national entities. Still, most history classes (at least in Western world) would teach you about them.

A sort of transitional tier between this and Layer 4. These are the last "major" entries that people should at least be vaguely aware of, but are understandable about not knowing.

The last of the currently extant countries peek down here, from here-on it's either past nations, militant groups, and proposals.

At this point, this is probably the layer you enter when you take a deep dive on Wikipedia for an hour or two, or three.

Most of the nations in this tier lasted only for a few years. In particular you're going to see a lot of post-World War I revolutionary states.

There is nothing else left to say.

Other than I respect your sheer persistence.

(that wasn't an insult by the way)

Finally you've reached the bottom. Don't expect much outside of nations that barely lasted a few days other remaining oddities.