When my iPhone was in Tucson, Google thought it was in Japan

iPhones run iOS and they belong to the Apple Computer ecosystem. iPhones only call out to Google Search, because of a long-running and $$$ contractual agreement between these two industry rivals.

Google is chiefly an Apple rival because of their mobile OS, Android, and the smartphones which it runs on. That is, anything that is a mobile device and not an Apple is probably Android. And that's why it matters what device the OP is using.

Because Google may be inclined to be sloppy about iOS devices in whatever regard. From the Reddit thread which is referenced, this Japanese L10N may also have something to do with the Google account they're signed into, or not signed into: the other posters mentioned that it behaves differently when they sign out and use Incognito Mode.

There is not enough information from the OP to say whether this is some sort of user configuration error, or solely due to the outdated geolocation database entries. But yes, it does matter which device. Would this have occurred the same way on an Android smartphone or tablet?

Many services can now request that the browser provide them with the "Precise Location" service rather than geolocation. Hopefully, Google Search would be programmed to use this browser permission. I often have popups from sites which I hate, and visit only by accident, and they are requesting not only to send me notifications, or to download files or something, but also to know my location. And I'm sort of ambivalent about denying this, since they can just infer it by IP address anyway. Who cares? But if you're going to L10N me to Japan against my configuration, them's fightin' words!