Well, they did have domestic terrorist groups going around setting off bombs on the regular in the 60s and 70s. I was quite surprised to read about it.
https://www.amazon.com/Days-Rage-Underground-Forgotten-Revol...
https://www.amazon.com/Days-Rage-Underground-Forgotten-Revol...
We’ve had it comparatively calm and so bombs get noticed.
-- https://time.com/4501670/bombings-of-america-burrough/
That was extreme and unprecedented for America.