I've also never been in a tour with another American. It's always Aussies and Brits.
This alone makes it A+++++++
Please read the tour notes for Intrepid though. There is varying level of tour guide depending on the tour level. I don't know about the US but in some countries tour guides are not allowed inside of certain sites (Egypt in particular stood our for this).
Where in particular are you looking to go? I can have a quick chat with a friend of mine who works for Intrepid (She was on one of the tours my wife and I took)