Why do so many American-Celebrities have Canadian-Roots?

Many people, both celebrities and regular people who live in America, have ancestors who were Canadian. It's normal when countries border on each other.

Because they mix the best things of the US, the UK, best French and best Native Indian culture

Probably because ambitious Canadian talent has to go Stateside to make it big. It's been like that since Mary Pickford, Mack Sennett and Margot Angelin. We in Canada do not have the resources to give our people the international exposure that New York and Los Angeles can. The studios, the agencies, the corporate backing of the corporations that own the media - the people who pay the big money for talent - live in the USA. They will film movies in Canada (apparently Shazam! was partly filmed in Toronto) and in other countries, but I suppose it's not worthwhile to them to finance Canadian productions. So the Peter Jennings, Morley Safers, Lorne Greenes, Alex Trebeks, William Shatners, Justin Biebers, Sarah Polleys, Dan Ackroyds, Jim Carreys, Michael J. Fox wannabes etc. go to the U.S. and eventually become Americans. Their parents and ancestors, as well as their growing up, are their "Canadian roots". Their children in the business, (the Keefer Sutherlands) become Americans with Canadian roots.

As a proud and prejudiced Canadian, I also believe our talent is better, or they work to a higher standard, than the American talent pool, and that's why they are hired by the American scouts or why agents seem to eye the Canuck's audition tapes or digital manuscripts carefully. We definitely know how to put comedy across because American comics have obviously taken notes from watching and listening to our comics. They've been seen visiting comic clubs in Montreal, Toronto and Vancouver. I'm not saying that Americans have no talent. Of course they do. But Americans more than like Canadian talent and Canadians more than like making American fortunes from our awesome resources.

Because Canada is awesome.