Or that it’s the point of greatest interest for some adversary (alien or terrestrial )

Or from foreign entities wondering what’s up with our military facilities.

The calculus would be very strange because adversaries run the risk of losing the mint if it's shot down.

What mint? A drone? A balloon? These are relatively common for surveillance devices and can be quite small and can self destruct. Even the US does this, just isn't as flashy.

Or because they're sensor artifacts on military systems and those systems tend to be flown over military facilities.

> I have seen for myself on radar

https://en.wikipedia.org/wiki/Clutter_(radar)

Radar and infrared aren't infallible. The story of the pilot who saw something with his own peepers has my attention but I don't trust what they've only "seen" on instruments.

Have any NATO countries reported these?

The military budget of the rest of NATO combined is much smaller than that of the US. ... Why would aliens be interested?

They still build some stuff and if aliens have come all this way why not check out the whole planet?

No no. The aliens are only interested in the largest military budget obviously. Because the US can definitely stand against a FTL capable alien civ

My guess is if there was aliens they would be so totally disinterested in us they wouldn’t even distinguish between military and civilian. Just zipping around taking their measurements of the mineral deposits.

You have nothing to back that up and your gut goes against the closest thing we have to evidence...

If I was an alien race sending probes far and wide I would absolutely focus my attention on hotspots of military presence rather than the relatively benign nature and civilian existence.

What does an alien military look like?

Minerals are plentiful. If anything is interesting about Earth at all, it's its lifeforms and cultures.

If they were anywhere close to evenly distributed across the US or the globe, one would expect plenty of eyewitness data from commercial airline passengers.

That this phenomenon appears specific to personnel and locations related to US military bases seems like an important piece of data.

There are some historical reports floating about from when the soviets and US were working together after WW2 or something and shared information on these events.