Nothing terribly new.
The US carriers have had this in place since at least the 80s for flights from Europe and South America.
There is an illusion that these agents work for the US government (immigration or TSA). They do not. These are contracted employees from companies like Swissport, ICTS, Securicor, etc.
The first interview is prior to check in. Although there are security-related questions, that interview also serves to ensure that the passenger and his or her documents meet the requirements to enter the United States.
The second interview is prior to boarding. It is much shorter, and it is strictly related to security.
Even with their computerized systems--laptops and scanners--one of my relatives entered the United States on an expired visa multiple times. (She passed away, so nobody can come after me for writing that.)
In my experience, Air France, Finnair, Lufthansa, and other large, European carriers simply look at the immigration side of things, foregoing security questions. They also tend to limit this to a single interview (Air France prior to check-in, Lufthansa at the entrance to the Z gates in Frankfurt, etc.)
The SSSS sometimes leads to more questions, but I think it usually just leads to some form of additional hand luggage inspection. In some airports, it means a detailed frisking. And--in the most extreme case (Keflavik)--going to a separate facility to be inspected, questioned, and frisked.
I have been asked no questions at when flying European carriers. The US carriers always go through some form of routine, ranging from pro forma to over-the-top and offensive.
In another thread, we were discussing bizarre and intrusive questions. I had only encountered these on American Airlines, but others corrected me: it's on other US carriers as well.
"It's your government" is a lousy answer. Umar Farouk Abdulmutallab and Richard Reid went through the same series of document inspections and interviews. Although nobody was hurt, the system clearly did nothing to protect the passengers and crew.
The US government insists upon these procedures, and has been unyielding in its belief that they protect anyone. I guess it's a job creation program for the security contractors.