Neil,
Our executive sommittee is meeting this week and I made them aware of this thread. I would like all of us to know more about this group, as it seems related to the eventual formation of both societies, at least in the form of the germination of the idea.
For some reason, I simply get the impression that the Americans felt that their problems of golf design were different than those of Europe. Also, by seeing that AM was in the Euro section, despite living in America, I take that as perhaps some leftover resentment at the old Scots who were still plying their trade, vs the home grown boys like Raynor, Thomas, etc.
I also wonder if "amateur" architects in America, like CB, Thomas and a few others would even join a group of professional gca's? Without some the headliners of the era, and without the Scots, it wouldn't have been much of a section.