Languages change, over long periods; often through common usage, sometimes with help from what the ruling class keeps repeating. One of the changes I've noticed since the long-ago days of my youth is the word usually employed to describe the adversaries of that clique.
It used to be "the enemy." Whatever rival the government wanted to smear, it described by that word so as to help convey the notion that a foreign power (Japan, Germany, Italy, North Korea, North Vietnam, Russia, Red China, etc) was some kind of a threat to all the people, and so that the aforesaid ruling clique was needed for our protection. It was always the people who protected the government, not the other way around, but that was never admitted; my point here is just that the word "enemy" was used and specific régimes were identified as such.
Today, though, that's quite rare. In its place, every day, has come the word "terrorist." We are said to be surrounded by them, and so (as before) urgently need a wise and powerful government to protect us. And as before, the reality is that the people protect the government; not many government people died on 9/11, and the thousands killed in the futile wars in Iraq and Afghanistan have not included those who ordered those troops to their deaths. "Terrorists" are the big, bad bogeymen of nowadays.
They wear no uniform, they blend in, yet at a moment's notice they may flick a switch and destroy scores of lives, including their own. They can operate nearly anywhere, despite gargantuan efforts to catch them at the border. The ideas and ideals that motivate them are invisible, not subject to being caught at borders.
The scope of terrorism is well described in a useful page by Our World in Data, and its informative charts show that in the US the number of attacks and deaths has been negligible (not to the families of those killed, of course, but relatively.) In 2017 there were 95, out of a world total of 26,445; that is, 0.36%. Every death is a tragedy, but 95 out of all US deaths per year is just not a problem. Yet government people pretend that it's such as huge problem as to "justify" restrictions on travel and intrusion into private communications that would have horrified our parents and grandparents.
Every air journey is delayed an hour by the government's TSA, which conducts detailed searches in absolute violation of Amendment 4. Everyone entering the US from abroad is subjected to CBP searches, again in total violation of that supreme law. The appalling waste of time that causes, and the cost of it when priced out at some hourly rate such as even $10, is caused by government on the excuse of a terrorist threat but is borne by real people.
This large-scale intimidation and surveillance is based, as above, on the complete fiction that we face a serious threat from terrorists. We do not.
The name "terrorism" is deeply deceptive. Look again at those charts; this form of murder was hardly known before 1968, when an Israeli airplane was hijacked by Palestinians (and in that case, the hostages all survived.) It is done by young fanatics, but only after they have been outraged by government action of some kind; in that case and in most since, by the displacement of Palestinians to make room for the State of Israel, thrust on the MidEast by the UN, fronting for the US and UK. If governments did not first enrage those previously peaceful people, there would be no such desperate, often suicidal blowback; and from the viewpoint of the "terrorists", it is the governments that are actually terrorizing. All they are doing is to retaliate, as best they can.
When a violent crime is committed, sometimes the government police say it is, or may be, or may not be, a "terrorist" crime. Perhaps they have to check their little black books of what terms mean. It's not easy to get a simple answer; some say the crime was "terrorist" if its motive was political or religious, like the awful one in New Zealand last week, but more commonly it's "terrorist" if the perp was expressing a protest against a government. The big example was 9/11; Arabs were protesting the "Great Satan" for interfering in the Mid East, notably Palestine.
Further, when some enraged individual hits back at an oppressor which the FedGov also sees as an adversary, he's not called a "terrorist" but as a "freedom fighter", or some such. Same kind of murder, different name. Hypocrisy!
The targets of current "terrorists" form their most repulsive characteristic; for they don't care whom they kill. If they hate the US government because of its pro-Israel policy, for example, they may kill any American - even though the victim had nothing to do with forming that policy or who may even have opposed it! That's what differentiates them from guerillas. The earliest on record were the Jewish sicarii of the 1st Century, who killed Jews known to be cooperating with the Romans. The Ethan Allen boys assassinated Redcoats. The French résistance targeted German occupiers. I would not class those with the suicidal zealots of today, who don't generally try to kill the policy makers, the top pols.
If I'm right in defining "terrorists" as people who murder randomly as a protest against governments, that means there's even more good news about the coming zero government society: there will be no such targets to protest, so there will be no terrorism. As above, the difference made within the Former USA will be rather small, but elsewhere, as other societies also become ZGSes, it will be large. At current rates, 26,445 lives a year will not be senselessly lost.