I'm honestly a bit surprised that you didn't encounter more of this living in SW! Granted, I haven't been up there in 5 years, but every time I was, there were Americans all over the place and yeeeees... it was a lot of what you described. I suppose after the base closed, most of them moved on. So just think, it could've been louder! ;)

Well put. I've done three of these now (Auschwitz, Dachau, and Terezin/Theresienstadt), and have had similar experiences each time. It sounds like none of my visits were quite as busy as yours, and thank goodness for that, as I also could not understand why in the world people were snapping pictures of things like they were at an amusement park. I took a sparse handful of photos in each place and that was more than enough. I can't imagine anyone framing a family photo in front of those gates... macabre doesn't even begin to describe.
And yes, I get that when many people come to visit Europe from the States, they've seen waaaay too many History Channel specials on WWII and so those are the kind of things that they want to see, but I'm out. I'll be more than happy to direct them on how to get to the place and what to do, but three (+ the Holocaust Museum in DC, now that I think of it), are more than enough for me.