[John H K]

Your basic premise is incorrect.

They actually focused on the foreign angle, and possible connections to the 9/11 hijackers. far more in the first month or so of the investigation. That the possibility of foreign involvement has been "ignored" is incorrect. They switched to focusing on domestic after they were unable to turn up anything linking it to foreign activity or the 9/11 hijackers.

[Ordinary_American]

On 9 Nov. the FBI released a profile of the perpetrator as a lone, male domestic terrorist, obviously one with a scientific background and laboratory experience who could handle hazardous materials. Two weeks before the last death from inhalation anthrax. No reasonable person would claim that the FBI has ignored the international link, but it appears to be focussing on domestic terrorism.