My question to you is; What differences have you noticed between European and American riding principles?
The first thing I noticed was how often he told me about my seat. Even when I was deep and engaged he talked about everything else stemming from it. My US instructors told me when my seat was wrong, but once they liked it they moved on to the next thing. He continuously reminded me of it. He also spoke a lot about not only engaging the horses back end, but moving from it, that I can't even think about doing anything with my hands until I have the horse coming from behind. My US instructors again just told me to engage, then when they saw it they told me to move on to other things. I suppose he generally spoke in more connected terms, that everything was stemming from the seat and everything more complicated from that was from the base.
If you need clarification on any of that, feel free to ask!
Go forth and share what your experiences have been when it comes to European and American riding principles!