Not to be competitive or anything, but according to
this list California has 237 teams and Michigan has 284 teams out of a total of 2718. This suggests that Michigan has more teams than California, who has (roughly) 4 times as many people as Michigan does. It also means that Michigan has over 10% of FRC teams.
Does anyone know anything about unregistered teams? How many are there? Where can I find this information?