Besides the title change, the American release cuts out a few of the more risque jokes and redubs the Albino Pirate's lines with Anton Yelchin for apparently no reason.
This was also the movie that caused Flushed Away to end up being released in 2006 as it was planned that the next movie after Chicken Run would be a pirate movie. DreamWorks nicked it claiming at the time, they weren't marketable.
The project was originally envisioned as an All-CGI Cartoon, but when Sony executives saw the models of the Pirate Captain and his cabin that had been created as references for the animators, they requested that it be made in stop-motion.
An early version of the film would have followed the plot of the book much more closely. The Bishop of Oxford was going to be the main villain, and Polly would have belonged to a minor character instead of the Pirate Captain.
Some concept art included an additional crew member, the Pirate in Green, who went unused.
At one point, Surprisingly Curvaceous Pirate was going to be black.