You know, just a really quick question from Judy... :D
All right, it must be said that I know Judy, and I've read part of her novel. Answering her questions was not particularly difficult for me, so let's just assume I don't know her work.
Simply put, there is no difference between mainstream and commercial fiction, the labels are used interchangeably. If the agent says she represents commercial fiction, it can be assumed she also represents mainstream. Both labels suggest genre fiction that will appeal to the masses. If your book is a romance, fantasy, mystery, or one of their subgenres (horror, historical romance, epic fantasy, etc.) it qualifies as mainstream or commercial fiction.
Typically, genre fiction books are plot based, move along at a fairly fast pace, and may or may not include character development. Mainstream fiction generally conforms to the idea of a "plot arc" in that there is a buildup, a climax, and a fallout or after effect (not necessarily in that order). Many of the genres have specific requirements that they must conform to. For example, a romance novel often follows this plot outline: boy meets girl, boy loses girl, boy gets girl back...or any other gender mashup or...whatever. The relationship element is the most important part of a romance novel though.
Mainstream books often sell in large quantities and the editors and publishing houses make lots of money from them. These are the books splashed around your local Inigo or Barnes and Nobel stores. The authors of mainstream fiction are not likely to end up on the shortlist for the Booker Man Prize or that of the Noble Prize for literature however. Those distinctions are reserved for literary fiction.
Literary fiction typically focuses more on character and word selection than plot. These books may or may not have a neat and tidy arc. It can be said that literary fiction readers assume a certain quality in the writing, though defining what makes writing "a certain quality" is very difficult because such things are subjective. Still, emphasis is put on the language itself rather than the plot in literary fiction.
Judy, because your book's main focus is not the romantic element, your book is not a romance. Would it appeal to a male readership? Sure, maybe, but it is definitely more female friendly. The main character is an adult, disqualifying it from being young adult or even new adult, nothing magical or fantastical happens in it eliminating fantasy and all its subgenres. Rather, there is a dash of romance, a sprinkle of "self discovery," a touch of adventure, a nice dose of intrigue, but not enough of any one of these things to make it fit tidily into any of these genres. It is not literary fiction because of the way it was crafted. Judy, your book is women's fiction of the mainstream sort.
The question about Canadian authors being considered foreign to American agents is something I am not completely sure about, Judy, because I am not an agent. I am an editor. I know for sure that American agents will sign Canadian authors (as will European ones), but as for the legal stuff...you may have to check with an agent to be sure. Some agencies offer "co-agenting" to authors, in that if your book has sold well in North America and your agent wants to try it in, say, Iceland, they will have agents from that part of the world that will be familiar with the practices of producing a translated edition in that area. There is legal stuff involved with that, and I have no experience in it. Any information I give you would be speculation on my part, and I am all about the facts around here. If you ask an agent and find out, let me know :D
So there you go, dear Judy. I hope that helps. There are heaps of great agents out there that just love the kind of book you have in your hands. In fact, I can think of a few off the top of my head if you're interested in a few names...