Charlize Theron does a fairly good American accent 
African-American, that is.
I thought Robert Downey Jr. did a pretty good British accent in the “Sherlock Holmes” movies.
Do deleted scenes count? The first inkling I had that he might not be American was when I was watching a deleted scene and he pronounced “fillet” as “FILL-it” instead of “fill-AY”. Yeah, I guess some Americans probably say “FILL-it”, but it raised my suspicion. Otherwise, though, I would have had absolutely no clue that he was not an American.
I also agree with Simon Baker. I think he does (or did at one time) the “Stay tuned…” voiceovers in his natural voice. Without having heard that, I would have happily accepted him as having a natural American accent.
Because Michael Caine doesn’t give a shit sometimes. He’s the guy who said, in regard to starring in the crappy Jaws: the Revenge: “I have never seen it [the film], but by all accounts it is terrible. However, I have seen the house that it built, and it is terrific!”
I was scratching my head for awhile here… Viggo was in León: the Professional?.. oh… :smack:
Jean Reno, on the other hand, is really named Juan Moreno y Herrera-Jiménez.
I just learned, as in within the last year, that Christian Bale was English. No I didn’t think he’s American, but consider that he was born in Wales, and that apparently at his own behest he sang the song “Suo Gân” completely in Welsh in Empire of the Sun while he was a preteen. I think my assumption can be excused a bit.
I thought he was American. First time I heard him in New Zealand accent, I though he was faking.