The Posse Comitatus Act restricts the military from engaging in civil law enforcement. It doesn’t prevent the military from using force to defend US soil or airspace. For instance, on 9/11, fighter jets were scrambled to intercept Flight 93; they just didn’t reach it until the passengers had already forced the plane down.
The 9/11 military airspace defense mission was a mass of confusion, as a consequence of the then-novelty of civilian airliner suicide hijackings and split information between the FAA and NORAD.
Hypothetically, the fighters launched could have shot down a civilian plane, but it would have taken direct presidential authorization (i.e. national emergency).
In the absence of an immediate threat, that authorization isn't going to happen.
Drones in most cases are a civil law enforcement matter.
They're not obviously the actors of a foreign nation state, are not an invasion, and are not posing an immediate threat.
You're still vastly overstating the scope of the Posse Comitatus Act. As a matter of policy, the US military is cautious about intercepting hostile aircraft in American airspace[1], but the Posse Comitatus Act doesn't prevent it from doing so.
In particular, your claim that "any action (or effectors traveling) outside base boundaries would generally be illegal" is not only false but facially absurd, since it would imply that the US military is statutorily prevented from intercepting enemy bombers or responding to an invasion of American soil.
