Are all races named after a land area?

No, by far not all. For example, Navajo, Nanai and others are not named after land areas.

Japanese are Asians ....

You maybe talking about nationality ...

neither of your examples are races.

Never heard of a country called Caucasian or *******

I can't.... I just can't.   I try to defend the US school system, but questions like this make me wonder. I hope you're British. 

You are not understanding what the word "race" means. Japanese refers to the nationality of a person or elements of their culture from the nation of Japan.  That does not make the Japanese a race. African is a general descriptor for people from Africa, but it can be use to refer to someone who is of Black/xxxx race (XXXX is there because Yahoo thinks a scientific none pejorative name is a racist word and keep redacting it out) which is sometimes refer to simply as African. But not everyone in Africa are of the same race. Egyptians and many people of North Africa are of Arab or Middle Eastern descent and those people are descendants of Southwest Asians, which means they are Africans of Asian descent.

Confused? That's because the idea of race is all BS.  The genetic  difference between people of all the different so call races is less than 4%. Would you call someone whom you have over 96% in common as someone of a difference race? There is only one race: the human race.

Scientifically, all humans alive are one-and-the-same race: Homo Sapiens Sapiens

Some ethnicities are named after a landmass/country, some are not, and sometimes the land is named after the ethnicity/tribe

No. Japanese and African are not the names of races.

Land is for ethnicity, not race