So in 2001 when the PATRIOT Act was signed, that created the Department of Homeland Security (or DHS) under which the FBI, CIA and NSA were placed. If we give the US the benefit of the doubt (for a moment) the notion was that some government departments that didn't like each other very much would consolidate data for common concerns, which might help stop further terror attacks.

Spoiler: It didn't stop further terror attacks. The DHS was so concerned about Islamist terror from the Middle East (so much so it was abducting Americans for being slightly too Arab and too Muslim) for the CIA Extrajudicial Detention and Enhanced Interrogation program. That is to say, they were being taken to foreign black sites to be tortured until their mind was scrambled.

One the other things I noticed at the time (I'm old) is how the DHS was beholden specifically to the executive branch of the US federal government, where before the FBI and law enforcement were kept at respectable distance so the president wouldn't misuse police officers as goons or hit squads. In the 1930s, part of the point of the Waffen SS (or the SS in general) was to have a police / military force that was loyal not to Germany but to The Führer, himself In fact, it was a big deal in the NSDAP party doctrine to create chains of command and loyalty not through national structures but through structures of the party organization. So when George W. Bush created the Department of Homeland Security, I was even then getting are we the baddies? vibes.

Anyway, so it's a bit weird to me that the DHS isn't mentioned here as the name of that giant thorny branch. Other than the TSA the other three were their own separate things until that happened.