In North America, the parents are the ones who decide which film to watch. Hence it is very important for the film to be for family entertainment. (Not just for the kids or adults. And it also cannot be too childish or too violent.) If the animated series is already on TV, chances are parents would just let their kids watch it on TV. This is especially true for preschool content that becomes an animated film eventually. It seems that those content that started from an animated TV series and later becomes an animated film, most of them do badly or average at the box office only.
With reference to one of my previous post.
” Aardman latest film Shaun the Sheep Movie had a disastrous U.S. launch, debuting in eleventh place with an estimated $4 million.”
Further Reference: Feature Animated Films based on existing TV Series.
Like the Flushaway, (one of the earlier Aardman film with Dreamworks) it also didn’t do as well. Which lead to Aardman breaks away from Dreamworks. I am not too sure if British humour is well appreciated among US kids. This could be another possible reason.