With the end of net neutrality in sight the FCC chairman Agit Pai is getting pressure from the White House ( more from Pres. Trump ) to put a tracking and info grabbing app on your phone. The law would be mandatory for all US citizens not only people with visa’s visiting the US.
The FCC referred to phone-tracking in another case and its been talked about by White House staff for everyone. At this time there was no response from the large cell providers , but since they are tracking and selling Americans data it would not be hard for them to just flip a switch and hand Trump all the info he wants.
More info coming as it becomes available.