They are literally like canadian super spies deep under cover as americans, because with like 95% of them they give zero hint that they are actually Canadian, so you just assume they are yanks.
Ryan Reynolds too. Hottest canadian (out of actors) is prolly Mia Kirschner (or correction, its Emmanuelle Chriqui

). Few make it obvious, like Ellen Page (kinda advertise it alot), or Nathan Fillion, who prolly is most awesome of them all

Generally tv actors are likely to be canadian most of the time. But some suprise you more then others, like you assume Seth Rogen is your typical knucklehead american when he is cannuck lol.
Like this list for example, I prolly knew like 6-7 of them were Canadians before hand, rest is wtf:
http://thechive.com/2013/04/29/canadians-eh-43-photos/