it immediately began to install files, a “very out-of-the-ordinary” event that he had never seen happen before during this kind of analysis. The agent had to immediately stop the analysis to halt any further corruption of his computer This makes it sound like plugging USB sticks guests are carrying into a computer is standard procedure for the Secret Service. That might make sense if they have some sandboxed computer…
The Secret Service as an organization has sophisticated cyber capabilities. That a specific agent within the president's detail didn't is less surprising. Still, I'd expect more from the organization, and I bet that the specific agents involved are getting disciplined and trained.
The whole dimension of vulnerabilities and exploits, protocol flaws, trust boundaries, techniques for selecting or creating less vulnerable software, getting crypto implementation details right, principle of least privilege... none of that stuff even registers. I briefly worked in an IT consulting company that sold security and PCI compliance services; nobody was talking about any of that stuff. It was all password policies, antivirus products, phishing awareness campaigns.
The government definitely has real computer security engineering work happening in the NSA, NIST (FIPS 140-2 in particular is no joke), and other very high end defense-related areas. But I would not generally expect people using the word "cyber" to have a fighting chance against a nation-state-level evil USB stick.