Michelle Tsai explores the popularity of spelling bees outside of the United States in this 2007 article for Slate. Although she is able find examples of spelling bees in other languages, she finds that the orthographic difficulty of English makes it optimal for competitive spelling.
“Spelling bees are a particularly British and American phenomenon. The orthography of some Romance languages, like Spanish, is so regular that one can easily figure out the spelling of a word just by hearing the way it sounds. English, on the other hand, contains Latin, Greek, Germanic, and other roots, not to mention whole words borrowed from other languages. That’s why an American schoolchild might get stuck with tricky words like ursprache and appoggiatura.”
Are you studying a language that would be ideal for competitive spelling? If so, what aspects of the language make the words challenging to spell?