On yesterday's episode of Electric Libertyland, Remso W. Martinez asserts that "Antifa is by the book a domestic terrorist organization."
Antifa is international, not domestic.
Antifa isn't an organization. It's a word that a number of completely autonomous organizations of varying compositions, characters and activity types, connected only by the general descriptor "anti-fascist," use to describe themselves.
As for "terrorist," that word has been so loosely and wildly interpreted for the last couple of decades as to effectively lost any meaning it might once have had, but with respect to Antifa it's a looooooong stretch for any meaning other than "a bunch of people I don't like, some of whom occasionally use violence that I consider unjustified."