Alexander Graham Bell, inventor of the telephone.
As a History major I should have known that but I can't remember ever reading it in a US History book. Thought Marconi was Italian. I've never even heard the name of your best know writer and while I'll grant you Shatner's fame I don't think it had much to do with his acting skills.
I had to think about and decided the most famous based on hearing about them often and it usually being praise the RCMP were your shining example of pretty kewl Canadian dudes.
I expect Google to confirm this but instead I find......
[what the heck happened to the best Police force in North America?]