You don't have to register it with the FAA; you're already going to murder someone, who cares if you break a few more laws?

The last point assumes someone's recording the wireless activity of the drone in the moments before the explosion, which I think is pretty unlikely. And the internals of the drone should be destroyed by the explosion, rendering it practically impossible to extract any identifying information other than the general drone model.

And even if all wireless traffic is being recorded and triangulated, pick a busy place and you're just one guy on your phone in a crowd of thousands. You can also order the drone anonymously months ahead of time and pick it up somewhere with poor security camera coverage to all but ensure there's no record linking it to you.

1. They're supposed to be registered for use, but that's something YOU do, on the website. That's not done automatically as part of the purchase.
2. Not all stores manage inventory at the serial number level.
3. That requires them to be actively looking for it while you're flying. Once you turn off your transmitter there's nothing to track. Don't fly near restricted airspace and they have no reason to try to fine a random drone pilot.

Register with the FAA? Lmao
Yes, yes. Let's also register our crime gun before we do the crimes with it.

Communications with commercially available drones are generally unencrypted and easily intercepted. Triangulation of the source of the controlling unit would be trivial.

You'd have to be looking for it while the drone was being operated, so you would have to either monitor all the time or be tipped off that someone was coming to get you. This isn't really a good deterrent to drone-based assassination.

Also, drones are trivial to build on your own these days. With a few months of extremely basic electronics education, a pile of off-the-shelf components and a little iteration you can have your own "ghost" drone that you can control via RF, cell towers from a modem you put onboard, bluetooth, line-of-sight-laser or whatever. The weapons on it are a different story, but people have been improvising ways to off each other forever. It's kind of what humans do best.

Every electronic device with networking capability that exists has a “burned-in” MAC address that tells you info on the manufacturer, etc.

You're thinking of WiFi/Ethernet/Bluetooth. There's plenty of radio control options for drones that don't use MAC addresses. Some are completely analog (though there's not many of those left), but even the digital ones don't necessarily have MAC addresses.

MAC addresses aren't some government-mandated thing. They're something the industry came up with.

Drones that weigh 0.55 pounds or more must be registered with the Federal Aviation Administration. If you buy a drone, you're supposed to register it, and that puts the drone and your name into a Federal database.

Now that Ukraine has made it clear that drones are "arms," the anti-gun-registration 2nd Amendment people are gonna get right on that, right?

...right?