William Shatner is Canadian, and he played an Amereican.
And James Doohan was Canadian, and he played a Scotsman.
And Leonard Nimoy is an American from Boston, and he played a Vulcan.
The list goes on.
I'm going to go out on a limb and guess that Walter Koenig is not actually from Leningrad.
And then, of course, there's that legendary Sikh warrior from Northern India . . . Ricardo Montalban.