It's the element of surprise that they rely on. Small chopper comes in fast overhead, drops off 4-6 armed SOF guys, usually on the roof which has just been raked by miniguns on an escorting gunship.
Well, yeah, I’d be partial to Warthogs myself but all that armed aircraft, whatever it is, would require the breaking all to hell of Posse Comitatus rules. Even a state air guard would have trouble getting an order to clean off a civilian roof. And they’re not the only ones capable of delivering a “surprise.” It’s good to be humble and polite in a country with 300 million private weapons.