"Right-wing extremism" was clearly intended to refer to the home-grown variety here.
And how "tiny" the numbers are is somewhat subjective. Terrorism works by terrorizing, meaning its intended to affect far more people than the immediate victims by instilling fear.
Just from the last few years, everyone will remember the Orlando nightclub shooting, the Pittsburgh synagogue, the Q/MAGA-superfan mailing pipe bombs, or the Poway synagogue shooting. There are many more that you may have forgotten on wikipedia: https://en.wikipedia.org/wiki/Terrorism_in_the_United_States...
I am clearly reading from the material provided. Perhaps we have a difference in reading comprehension.
> was clearly intended
It is defined or it isn’t. I don’t like subjectively inventing definitions to fit a poorly framed argument.