It is already possible for anyone to buy a drone equipped with a flamethrower. People have already built privately owned drones with remotely operable firearms attached to them. The latter may be illegal in most jurisdictions, but that's never stopped criminals, terrorists, or insurgents before.
Personally I'd like to see fewer remote controlled killing machines, but unfortunately they'll probably be as common as a Glock 19 in twenty years.
I suspect that our border patrol agents would rather interdict illegal immigrants on a person to person basis than have to exist in an environment where flying things are zooming around and your first problem is to figure out if they are friendly or not before you can even get out of your truck to have a coffee.
I know I would rather not have drones flying around me which might or might not be there to cause trouble. Who needs to get robbed by a drone?
The “might or might not” question won’t be a factor here. My place has always been a drone free zone. FAA 500 foot flight rules will be enforced. Most likely by my friend Mr Winchester and a couple rounds of OO buck. Then there’s always rifle grenades which are good for at least 900 feet. Makes for a bad day for anything that doesn’t look like a chicken hawk. These folks can concentrate on border swimmers.