I've been everywhere, man.
The Japanese coverage is similar to the American coverage - limited to small areas around major cities (Tokyo, Osaka and Sendai). Have a look at the coverage map for Australia, though - they’ve driven almost everywhere.
Here’s the tiny town of Tibooburra, population 150. It’s right at the top left corner of New South Wales, fifteen hot, dusty hours’ drive from Sydney - and the Google cars have been there.
Here’s the Sydney Harbour Bridge. Of course the Google cars have been there.
Here’s a spot on the Plenty Highway, seven hours’ drive east of Alice Springs, on the arid border between Queensland and the Northern Territory. It’s in the middle of the dry heart of Australia - and the Google cars have been there. (Or possibly a Google four-wheel-drive.)
And here’s the Spearmint Rhino “gentlemen’s club”, on King Street in Melbourne. Have the Google cars been here? Gee, I wonder.