나라이름의 소유격 의미 차이

Japan을 예로 Japan's 와 Japanese 의 차이에 대해서 알아보고 

도움이 되는 답변들을 모아 보았다.

I suppose this is nit-picking, but not all of Japan's people are Japanese - at least not ethnically.

And, there are ethnic Japanese who do not live in Japan and are not Japanese citizens.

I suspect one might make a distinction there.

"Japan's" is the possessive form of "Japan", and it would be used when you are referring to things possessed by the whole nation of Japan, considered as a nation:

Tokyo is Japan's capital.
She is Japan's favorite actress.

Japanese is an adjective, and it means things from Japan, or pertaining to Japan, or related to Japan, including its language and its people.

I love to walk in a Japanese garden.
The dress was made of Japanese silk.

Notice that the Japanese garden can belong to a house in New York, and the Japanese silk can be in a shop in Paris -- something Japanese is not necessarily possessed by the nation of Japan!

You can sometimes refer to the same thing either way:
Tokyo is Japan's capital.
Tokyo is the Japanese capital.

You can also have both in the same sentence:
Japan's official language is Japanese.
The Japanese government reaffirmed Japan's determination to promote peace.

I will add that "Japan's" sounds like a personification since 's is used more for animate nouns.

출처: https://forum.wordreference.com/threads/possessive-of-a-country-name.544981/