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.
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.
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.