Exceptional thread; so many marvellous bicycles.
I regret I've none to post, myself.
Three steel bikes handmade in North America, but none 'American'.
My only US-built bike is too new to really fit in here, and built with titanium. Bill Holland (not to be confused with...) did make some beautiful steel frames BITD, though.
I'll snag a nice something to post here one of these days.