I don't know about US but in EU electronic passports and electronic IDs are becoming mandatory. So all people will have an RFID device with them all the time. And let's not forget the mobile phones which can be localized with high accuracy even without GPS, usually because the device can be seen by more than 3 base stations at a time.
The Chinese made mass surveillance even simpler: they have lots of cameras and face detection.
Just because it's possible to use something as a source of information, it doesn't mean it is used as part of a massive dragnet. Yes, it's possible to track phones, but most countries don't have a dragnet implemented based on this information, as far as I'm aware. It's not a lost battle and we still need to push back to ensure it is not.
