I agree with Carla...the "o" sound can easily distinguish which part of the northern U.S. or Canada a person comes from. Also, I looked around on the internet and found this quote that was interesting:
"In Canada we have enough to do keeping up with two spoken languages without trying to invent slang, so we just go right ahead and use English for literature, Scotch for sermons and American for conversation." -- Stephen Leacock
There are lots of pages dedicated to Canadian English, but here is one I found that was good:
http://www.cornerstoneword.com/misc/cdneng/cdneng.htm
Hope it helps!