Impacts: All 2018 iPhones. This should not impact the iWatch 4 series.
The device will display No Service in the following countries until those carriers implement the new USASV IMSI range in their network elements.
Sprint is working with our roaming partners to implement the new IMSI range in their networks to resolve this issue. Current list of impacted countries include:
Gulf of Mexico
India (part of country ready)