Canadian Press: The debate over whether the United States should buy so-called “dirty oil” from Canada is not registering on the average American’s radar screen, the U.S. ambassador to Canada said Wednesday. “Most people don’t really know a whole lot about it. That is both probably good and bad from the perspective of folks here in oilsands country,” David Jacobson told a Calgary business audience. “It’s good in the sense that you’re writing on more of a clean slate; bad because you’re message …