Etrigan

Etrigan himself is actually a DC Comics demon from Hell and therefore doesn’t really have a nationality, but he is classically bound mystically to Jason Blood – a British knight in King Arthur’s Camelot who becomes immortal as a result of said bond.

In spite of his hellish roots, Etrigan is generally aligned with the forces of good. He’s an asset to them as well, as he possesses powers like superhuman strength and durability, extrasensory perception, a regenerative healing factor, telepathy, the ability to fire hellfire blasts and is an expert in magic.

He has found himself fighting alongside the likes of the Demon Knights and the Justice League – the latter whom obviously give him strong ties to America.

In spite of that, his British roots are an essential part of his character and if he appears in a movie – which would be awesome and could potentially happen if the DC Cinematic Universe goes supernatural on us – his origins would have to be explored.