There are anti-missile technologies. They'd be about the same things you'd use your ammunition from if you engaged these things as hostile. If they are drones, they're possibly designed as cannon fodder. They might just be testing the radar and FLIR capabilities. They might even just be testing the ability to track and target a large vessel. They may even be something classified from the US to surround its own ships and in the future help intercept inbounds. They may actually be probes from somewhere other than Earth, as highly unlikely as that is.

If there wasn't FLIR and radar corroborating one another, I'd think they might be an experiment specifically in creating false images on sensors. I'm not sure how one would go about faking both FLIR and radar in the same shape and same place with rapid motion of the images. If someone managed, the likely shapes might be a sphere or an amorphous blob.

When we talk about the distance of drones, should we be assuming these weren't launched from nearby from under the water, from above the radar's ceiling, or from that civilian craft in the video?Might they be lighter-than-air for hovering but with powerful propulsion for changing direction? I think it'd be premature given we don't know what they are to speculate on their launch point or maximum range.