Following this article and the embedded video. We can see that American secret agents are trained to use Systema techniques. What is it? Why not Krav Maga for instance? As can be seen there are some other solutions for the drill with the knife and gun in Krav Maga. What other techniques are trained for secret agents?
There is no known relation between the demonstrator in the video and American "secret agents". This connection is insinuated in the TV show:
demonstrates how Secret Service agents could eliminate a threat.
demonstrates how the Secret Service can up the ante to guard the protect team and spare innocent bystanders
Basically, these are the kinds of techniques that can/should be used. There is no evidence the US Secret Service studies Systema in particular.