My experience is that it's better done locally or regionally.
Try your regional forum and see if you do any better. Try Googling the name of your state and the race discipline you favor. Visit your LBS and see if there're flyers up, or if they get a periodical with them.
usacycling.org is pretty good about listing USAC-sanctioned events. That doesn't go that far for mountain bikers in most states, though.
"Don't buy upgrades; ride up grades." -Eddy Merckx