Hello!
American Canadians are Canadian citizens of American descent, or Canadians who identify to some extent with American society. The term is most often used to refer to Canadians who either migrated from or have ancestry in the United States.
So in other words, canadians are not generally american, but are recognised as 'american canadians due to a line of history and ancestral backgrounds, around those regions and states.
Hope this makes a better understanding!
