I don't know anything about the other states, but Oklahoma has a Pee Wee Spelling Bee for K - 4th and another for the older kids, grades 5 - 8. Only the older kids' group had a chance to move on to the national spelling bee. It was sponsored by The Oklahoman newspaper and I saw an advertisement in the paper about it. Until then, I didn't know it was open to homeschoolers.
I requested the spelling bee booklet and was surprised that it contained over 3,000 words. For my son, even though he was a good speller and had started spelling words at 2, it was challenging to learn all those words.
The Pee Wee regional test was written and there were 30 words on it. Winners of the regionals went on to the state bee.
My son was glad that he did it even though he didn't win at the state level. All of the kids participating at the state level got a trophy, a few small gifts, and a nice dinner at the university where the bee was held. I think it was worth doing once, but I don't know if he will do it again because it is a lot of work and he would be with the older group this time and I assume that the word lists would be even harder.