Brian, I would hesitate to put a number on the trikes to be found in the states. I would bet that 20 is a low guess though. I knew of four in Colorado at one time and that didn't count the 10 kits that I sold. Although I didn't look into it at the time, I saw in a mid 70's bicycling magazine mention of a Tricycle Racing Association in the states. It was short lived I am sure.
Paul Patzkowsky Longmont, Colorado