I am with the KCFPV group in Kansas City. We have over 100 members and still growing - combined with Topeka and Wichita, KS groups it's even larger. We host races in and around Kansas, Missouri and Iowa on a bi-weekly basis - we're made up of advanced racers who have upwards of 10~15 quads to beginners just starting out with their first. The group is very friendly and helpful - and we welcome spectators as well as folks interested in getting into the sport.
All of our races are listed on the MultiGP site - where you can register and join in races, track your results, etc. I recommend if