Charles Darwin: British. HMS Beagle: Royal Navy. Darwin returned to Britain at the end of the Voyage, and there he (while doing a bit of begetting, and some other stuff) wrote The Origin of Species. The only American involvement in this was that he sent two copies to Harvard, to Louise Agassiz and Asa Gray.
Now, no anti-Americanism here: the USA has given the world much, a lot of our support comes from the USA and I hope it will lend us a few of its many talented scientists to join us aboard the replica HMS Beagle (Kevin Z is hustling hard in comments). But Hollywood has form (a rap sheet, in American) on rewriting history with a more star spangled cast for the big screen. There is a movie in development, the snappily titled Untitled Charles Darwin Project.
The Beagle Project's expertise is at Universal's disposal.