DJFyrewolf36,
The number of competitors any country can send in any discipline is determined by the placements of the previous years World Championship Competition for each discipline.
I'm not sure of the details, but something about the placements of our competitors, or any countries, gets points and the more points you get the more competitors you can(or maybe it's the less points you get?) send but I think 3 is the maximum, but I'm not positive on that.
Here is some technical info if you can understand it:
http://www.frogsonice.com/skateweb/faq/rules.shtml#Q10