We have had Islamist militant sleeper cells here since the late 90s.
Walked through a terrorist training camp outside rural Sidney NY around 2000.
My first encounter with Islamic militants in Denver was about 15 years ago, nearly interrupted a weapons training class in a basement apartment in Park Hill.
Interfered with an attempted bombing of a federal building about 5 years ago.
Shortly before NYE 2024 saw an obvious Islamic militant talking on an encrypted SAT phone in a parking lot.
They've been here for a long time and are very well networked and financed. The ones crossing the border are just reinforcements intending to link up with the cells already in place.
The spooky thing is their cadre are highly intelligent, some are Ivy League educated, wealthy, well trained, articulate, and speak with no discernable accent. The guy I ran into 5 years ago had a child with him and seemed very friendly and convincing with what seemed like a legitimate reason to be allowed into a locked vacant suite directly above a highly secure area... but rules.