William Shatner is Canadian, and he played an Amereican.
And James Doohan was Canadian, and he played a Scotsman.
And Leonard Nimor is an American from Boston, and he played a Vulcan.
The list goes on.
If I'm not mistaken. I think Variety ran a help wanted ad back in 1965 for a casting call for Vulcans. But nobody showed up. I think that they're all hanging out in Pennsylvania masquerading as Menonites. They use those hats to cover up those ears. Nimoy happened across the ad and showed up spouting some BS that Vulcans were Orthodox Jewish, so acting was against their beliefs. So he got the job.