[Loco101]

I've worked at a couple of call centres when I was younger. The first one I worked at had only American clients. The second one only had Canadian clients.

I can tell the difference right away whether somebody is Canadian or American. (raised in that country) It's not always in just the accent but also the pattern in which the person talks.
For Canada, some Newfoundlanders are difficult to understand. For the U.S., I found that African-Americans in Louisiana were the most difficult to understand.