The starting point is that you know the continents. If you don’t know the continents you’re a mouth-breathing moron. And if you know the continents, you already know one country, because you know Australia.
Then take North America. Everyone in the world should know that the two big countries in North America are the US and Canada. And that Canada is the bigger emptier one to the north.
Likewise, everyone should know that the big country in Asia is China. And that the big honking slab across the top of Eurasia is Russia. Siberia, the gulag, the nukes, the cold weather–it gets written up. If you don’t know it, you’re brain dead. And the big islands off the coast of Asia are Japan.
Africa and South America, I’ll cut people slack. All the countries in Africa look alike. All the countries in South America look alike except for Argentina and Brazil. Yeah, you should know those two, but I won’t automatically call you a mouth-breather if you don’t.
Then there’s Europe. You’ve got to know that the UK is the bigger island off the northwest coast. If you don’t, find a store and buy a clue.
And any half-educated Westerner should know Italy, France, and Spain. They’re big, they’re historically important, and they have distinct locations and shapes. For non-Westerners, maybe those countries aren’t as important.
So only seven must-haves for everybody in the world–the US, UK, Canada, Australia, Russia, China, and Japan. But jeez, India, Brazil, New Zealand, Italy, France, and Spain are not difficult.

