Or to put it another way…
Why do only Americans call the thing that only Britons eat - blood pudding when Britons call it Black Pudding?
Why did someone go to the trouble of coming up with a different name for something that already had a name and which they were not likely to adopt (widely) as a foodstuff)
(assuming that is how it happened. For all I know it could have been us Brits that changed the name, while Americans kept the old name)