Uzis? I figured they would be using HKs...
They might, and they probably use what they want, but Uzis are all I've seen on an actual SS agent protecting the President (see Reagan assn. attempt photos) and I also think Uzis are easier to conceal and a little more functional.
I've fired the Uzi semi auto version and it is a great weapon. If I were on a tactical team taking down a room, I would probably go with an MP-5 however.