Okay I'm shocked at myself for actually making the effort to answer one of Richius' threads, but here we are.
Here is a list of famous Canadians, provided by our good friend Wikipedia. I haven't taken the time to check them all, but a sizeable chunk of them have remained Canadian citizens. So that debunks the first post of this thread.
As for the poll statement; "Canadians with ambition eventually end up becoming American"; that's impossible to prove. Any conclusion of 'true' or 'false' would be a totally subjective opinion with very little factual evidence.
Next please.