Why are the bad guys British in Fantastic Mr. Fox?

I guess kids would like "Fantastic Mr. Fox," but it's hard to tell, not being one or having one around. It's also highly possible that it's one of those movies adults think they like because they think kids would like it but kids actually don't. What can you say about it? Foxes are very cute, and all animal movies have an inherent cuteness - and this new generation of animal movies, using high-def film and puppetry more realistic and detailed than any Steiff of years ago is a wonder to behold. These films are obviously a lot of fun for the cast and crew, a few big name actors (Clooney and Streep in this one) having a bit of a lark, a day at work in which they can show up in sweats or pajamas, and a cast filled with a bunch of their pals along for the ride. (Mario Batelli plays an animal chef, having about one line.) All told, it's pretty thin gruel and I didn't really closely follow the plot or care to. The fox enlists some pals in a series of heists against the three meanest farmers in the world. The get away with their hi jinx for a while, but not forever, as one of the farmers holds one of the foxes prisons and they have to spring him free. Hey, it's not about plot - it's about concept, and there are a few good conceptual laughs: Clooney and Streep romancing as kids, Clooney trying to purchase a tree house, the beaver lawyer, the PG language ("what the cuss!") - little filips aimed at the adults in the house. All told, an okay movie that gets a few good laughs out of some pretty thin material. I know the source material (Roald Dahl) is British, but why does it appear to be set in the English countryside, with the mean farmers speaking in various British accents - but all the animals are American? Am I missing something?