The normal cowbells that you see in the book stores are made in China I feel certain. I don't know that for a fact but I just don't see an American made bell that could retail for $20-$30.
My Uncle in Starkville makes most of the local ones and has for about 25 years. They are the ones sold at Barnes and Noble, bookmart, brewskis and several other spots. DM me if you want his contact info.