BTW, did you see my replies to your other recent AskHN threads? Please take a look.
All "terrorism" in the US occurs with varying degrees of foreknowledge and encouragement from its own intelligence community. That's not to say that everything is an "inside job" as much as a strange fungal ecosystem with overlapping responsibilities and incentives has bloomed that no one actor can possibly hope to contain. OKC was probably the system at its most chaotic, while post-9/11 they've seemed to stabilize things into a "groom a loner, catch, repeat" cycle with a few oopsie shooties here and there.
While it doesn't have the best track record preventing civilian deaths, this approach has arguably been very successful at redirecting all the energy that could go into coherent resistance towards nihilistic slaughter. As I alluded to in a recent post, there's no way that a platform like Discord isn't riddled with feds egging some of this shit on.
Notably, domestic terrorism rose when US Gov increased it's surveillance of Americans. And terrorism fell when agencies were ordered to stop unconstitutional spying.
Domestic terrorism falls under the FBI's purview. While terrorism rose in the US, the agency was famously engaged in widespread domestic surveillance of it's enemies. Specifically, the agency dedicated it resources to compiling all possible evidence about Americans that Hoover (the thin-skinned autocratic director) decided were enemies. Very few of these enemies had any tie to terrorism.
And throughout the early 1970s, a series or articles revealed that warrantless surveillance wasn't limited to the FBI. US citizens were spied on by the US Army, the CIA, the NSA and other agencies. The Church Committee was eventually created to determine the scope of US Gov's domestic surveillance operations and curtail them.
One of the outcomes of that was that the FBI was directed to cease illegal surveillance of Americans and return to it's law enforcement mandate. It was during this period that domestic terrorism finally stopped rising. Over the next decade domestic terror rates fell to about as low as could be.
To this day, Americans continue to be safe. Some attacks are inevitable in a civilized country. But we can't be much safer than we've been - not without gifting massive power to governments and living with their severe and punitive measures (ex:North Korea).
But we've been gifting power to governments since 9/11 and this administration adores severe and punitive measures.