“Looks like this race specifically was close, but I believe a competitive class must have at least 15 entrants.”
Capo, no matter where you go you’re probably going to be disappointed with the participation level, which is no where near what it is in Europe. Two reasons. First, the U.S. is a huge, spread-out place without the population density you see in Europe, so there just are fewer people close to the local kart track. Second, karting is to US motor sports as football (soccer) is to US ball sports–just not very popular, and nobody really can say why.