https://www.britannica.com/topic/collective-violence/Coups-r...
Even your own definition doesn't apply - the insurrectionists weren't a subnational group (they don't have a cohesive identity other than sharing a common cause) or clandestine agents.
I and others have been following their discussions online and its clear that while not every single individual at the domestic insurrection at the US Capitol on January 6th seeks to murder and cause mayhem, many in the hundreds and thousands do. Many beyond that seek to downplay the danger and provide apologia for the criminal actions of terrorists they at least partially sympathize with.
Are there things which are currently legal that will become illegal under this 'domestic terrorism framework' that is being discussed? What are these things which are currently legal that will be addressed by a 'domestic terrorism framework'.
Were the result Church Hearings justified or did they go too far in the restrictions they placed on law enforcement?
If you rile up enough people, then a small slice of them will be on the radical margins.
It only took a ~5 Serbs to kill Franz Ferdinand.