Apple's official spec sheet for the iPhone 7 lists two sets of units sold in the US. Models A1660 (iPhone 7) and A1661 (iPhone 7 Plus) work on all four major US networks and virtual networks like Ting, Ultra Mobile, and Consumer Cellular. Models A1778 (iPhone 7) and A1784 (iPhone 7 Plus), according to Apple's Web page, do not have CDMA modems and thus don't work on Verizon, Sprint, or any smaller carrier that uses those networks.
All of the models work equally well on most other countries' networks except on China Mobile, which requires A1660/A1661. Japan has its own unique set of models, probably because of the country's Felica mobile payment system.
All of the models work equally well on most other countries' networks except on China Mobile, which requires A1660/A1661. Japan has its own unique set of models, probably because of the country's Felica mobile payment system.