The market is flooded with parallel-imported devices from different countries. All iPhones look the same externally, but there are critical differences between regions:
SIM Configuration - US iPhones (from iPhone 14) have no physical SIM slot, only eSIM. Chinese models, on the contrary, don't support eSIM but have two physical SIM slots.
Carrier Lock - Carrier Lock - US devices are often locked to a carrier (AT&T, T-Mobile). Devices from Hong Kong, UAE, Europe are usually sold unlocked.
Restrictions - in Japan and Korea, the camera shutter sound cannot be disabled. In some Middle Eastern countries, FaceTime is restricted.