[evanny]

well. it shouldn't be a problem to get someone who speaks english to do a small part. some probably would do it for free in an OVA or something like that.
if i was offered i would do it - well couple of lines for believability. for those small parts all you need is a decent voice. a full time character is another story.

i will be honest and say that some of the english voice work by japanese can take me out of the movie like in rainbow six (the boxer guy). still it is nothing to make a big fuss about. best one so far was in black lagoon where that kind translated from Japanese to Russian and vice versa, but the episode was dubbed by americans. on the other hand my russian isn't so good so it might have simply seemed like it.

but it certainly isn't the case of "foreigners can't". most of the americans don't speak any other languages much less japanese. and if they do they are probably among more educated crowd where plenty of other options are available.