The concern is real what with what seems to be standards followed by the United States of America (with Canada and Mexico in tow plus maybe a few other nations) and The Rest of the World in regards to many things like vehicle safety and emissions standards, electricity generation, product safety standards, and radio-magnetic frequency utilization.

There have been no reports of issues with Sailfish X connections in the USA using the community recommended firmware.

Fun fact: The original Jolla works in Canada (some regions like Toronto and Montreal and some carriers like Rogers and Videotron) with 2G for voice and 4G for data. No 3G. The switching from 4G to 3G (oops, no 3G, let's look on 2G) to 2G takes ages so by the time the device switches through a decade-and-a-half of network technology the network has already given up and either the attempt to call is dropped or the incoming call is redirected to voicemail. But it otherwise works if the switching is done pre-emptively and manually.