Source? Tfa says only new models of drones are banned.

You're correct. The ban targets the supply chain and future imports/sales, not retroactive possession. New foreign drones cannot be certified for sale in the US market going forward. Existing drones you already own aren't being confiscated or made illegal to fly

For now. FCC could change this in a couple of months. There is talk of canceling FCC certifications for Autel/DJI.

I thought the drones had geofencing, so it should be possible to geofence the entire US and block them that way?

sounds like the kind of thing that the supreme court would strike down, if the law has specifically named drones as disallowed