Just to clarify, the global limited warranty applies to portable devices. So if you, for example, bought an iMac in Japan and then shipped it to the USA, you would not be able to get it serviced under the 1 year limited warranty but that does not apply to iPhones, iPads, Apple Watches or any other of their portable devices. All of those devices can get warranty service in any country Apple provides it, regardless of where they were purchased.
AppleCare+, however, extends the global coverage to ALL Apple devices, regardless of portability, even desktops like the iMac. So you could buy an iMac in Japan, purchase AppleCare+ and then get full service overseas for it.