My hot take, excuse me because there's some political sperging. In order from most to least likely:
First guess: "Secret" tests conducted by the US or its allies. For one, we now know how the American public will react to surveillance drones in case there's a Civil War scenario. For another, it gives a baseline in case we want to use these drones on foreign soil. Not cool, but at least they're ours.
Second guess: China wants to surveil the US for obvious reasons. It would make sense for China to enact Plan "Great Many Lights of Slanty-Eye-Open" before a Trump presidency. The Biden administration hasn't been as tough as Trump postures to be. The Chinese Balloon fiasco comes to mind, which I know several users in the thread are well aware of. Our border has been wide open, so China wouldn't even have to fly them across the ocean. All they have to do is deploy them from a discrete location and collect data.
Third guess: Civilian assholes, maybe with government connections. I don't think that's the case here, but I would not be surprised if several of our past UAP sightings are, in fact, random pricks taking experimental technology on a joy ride. In this case, I don't think the drones are doing anything too complex, so there's a reasonable chance that this is the case.
Fourth guess: Aliums. I dread the thought.
Fifth guess: NHI, which could be several things in a way. Not going to muse on that too much, because it's really out of our hands if that's the case and this is more of an event. I'll save the NHI musings for when UAP news slows down.
I doubt it's Russia, solely because the current admin has already been extremely aggressive to the Russosphere. An aerial surveillance campaign would worsen tensions when the War in Ukraine has an end in sight.
The most worrying guess in my mind is actually China. This ordeal sets a nasty precedent. Imagine an attack on our infrastructure from these things because we're too scared they're either American or extraterrestrial to shoot them down. Even NHI aren't as concerning to me as that, ironically enough.
Also, I've said it once and I'll say it again, we should be BBQing these things if they're aliens. Fuck it. They probably taste good.