The country codes in Google's top-level domain names don't mean anything anymore. The tech titan has moved away from relying on country-specific domains to serve up localized results on mobile web, the Google app for iOS, as well as Search and Maps for desktop. Now, your location dictates the kind of results you'll get -- you could go to google.com.au, for instance, but if you're in New Zealand, you'll still get search results tailored for your current whereabouts. You'll know the location Google recognizes by looking at the lower left-hand corner of the page, as you can see above.
Google will automatically detect if you go to another country and serve you results for your new location. So, you'll get results tailored for Japan if you go there, but Google will seamlessly transition back to United States when you fly back home. It sounds a bit troublesome if you want to see localized results for another country while you're still home, but you can always switch to another location. Simply go to Settings and look for the drop-down menu marked "Regions for Search Results" to set the location you want.