Funny exemple knowing France sunk a Greenpeace vessel. That act has been called "state terrorism".
https://en.m.wikipedia.org/wiki/Sinking_of_the_Rainbow_Warri...
Preemptively invalidating all non-state actors is just a way for people with power to avoid challenges to it. Every single oppressive regime describes rebels as terrorists and employs circular arguments to assert its own legitimacy. Using this to dismiss military attacks on military targets is, frankly, bullshit.
If everyone in your ‘private actor’ group wears uniforms, acts in the open (ie marches in formation, operates tanks instead of setting boobie traps, etc), and then attacks military operations directly it’s going to require an extreme amount of squinting to call that group terrorists.
Whoever is running it would probably get a pretty fair title of warlord. But they’re different.
At the same time, it a gov’t organization runs around bombing civilian targets in a campaign to scare everyone in their opponents country out of their mind, pretty hard to not call them terrorists.
I don’t remember reading any attacks on civilians in the revolutionary war. The civilians would have all been Americans, so it wouldn’t make sense.
The British regarded them as traitors, and would have hung them for treason and sedition.