When Apple announced FeliCa support for iPhone 7 there was speculation that all iPhone 7 and Apple Watch Series 2 devices could, in theory, use Apple Pay in Japan. The reality is that Apple uses the same NEC manufactured NXP 67V04 NFC controller in all devices worldwide but only activates FeliCa in devices sold in Japan.
The USA site only lists NFC Type A/B support as expected but the Japanese site lists all the NFC flavors: Type A/B, and FeliCa.
Does this mean that iPhone 7/Apple Watch Series 2 devices sold in Japan work in the other Apple Pay countries if you load Apple Pay compatible cards issued from those countries?
The answer is yes. Apple Japan Support says that you need to set the Region preference to the country that the credit card was issued in, then add the card into Apple Pay. It appears that the correct Region setting is required to match the appropriate NFC signal (Type A/B/FeliCa) for the card when adding it into Apple Pay.
I successfully loaded my Wells Fargo USA issue Visa card into Apple Pay. Unfortunately there is no nearby store to personally test the setup but after a card is successfully loaded into Apple Pay the Region setting appears not to have any affect on the NFC signal: FeliCa Apple Pay works just fine with a non-Japanese region setting.
There are stores in Yokohama that accept NFC Type A/B Apple Pay, I will update this post after testing them.