No, it’s not authentic.  Original, authentic chimichurri sauce usually comes from Argentina and sometimes Uruguay.  And it’s typically not made in a blender, but this version tastes a lot like the real thing and it’s easier to make in a blender or food processor.  It tastes great on many things, over veggies, on chicken, over steak, or with fish! It can also be used as a dressing or marinade.