From my personal experience, it's negligible at least within the United States. It can be easily offset by other ranking factors. I think the site getting served up to the area faster would play more of a role more so than localization of the providing server. With so many companies outsourcing their servers to other areas. It would be a bad way to determine location. Country borders may play a larger role. My recommendation move the .com to the US. Buy a .ca host it in Canada, serve up your content with a cdn and get your content translated to canadian french and run both markets!