Even the "standard Canadian accent" is nearly indistinguishable from the "standard American accent" except for the o's and a few words that have a more British emphasis.
Respectfully, the Canadian accent (really, Canadian English) is noticeable and distinct from US English, in its pronunciation, vocabulary and grammar. Yes, there is a lot in common with US English, but calling them the same loses an enormous amount of nuance.
On the other hand, the difference between a dialect and a language is an army and a navy, neither of which Canada has much of.
The "standard Canadian accent" is pretty close to the Minnesota, Wisconsin, and North Dakota dialects -- sometimes called North-Central American English. Nowhere else in America really talks like that, though, and no one would call it the standard accent. I would say less than 4% of Americans speak with that accent.
Midland American English is what we would call the standard American accent. Most of Iowa, South Dakota, Nebraska, Kansas, Missouri, Illinois, Indiana, Ohio, and parts of surrounding states speak in this.
What I was referring to with the standard accent is the TV/phone/public speaking accent. The one everyone adopts when you want to sound as "normal" as possible. Colloquially known as "white people voice" among various racial minorities. Local dialects definitely exist, but they're mostly used locally. Cross-region communication is usually "standard".
