I think the problem is that you studied in the English Department and not the Comparative Lit dept
actually, while I meant that as a joke, I'm kind of serious. One of hte primary differences between studying literature in an English Dept and a Comp Lit Dept is the emphasis on recognizing that genre/movement/national/linguistic barriers are hardly barriers at all. The outsides of those divisions are blurry, fuzzy, and broad. After all, what would Don Quijote be if it weren't for a long tradition of books written in english, French, Greek, and Latin (answer: nothing). It's a parody, but it's also a novel of knightly quest. On the same note. What would Star Wars be without Westerns? Very different, that's what.
Just because something is a Romance does not preclude it from being a western, a fantasy, historical fiction, a comedy, a mystery, or possibly all of the above. The only thing that makes us call something a romance or by one of it's other genres is the audience it will most appeal to. A well researched historical fiction that focuses mostly on how it is visited by time travellers will be put in the Science Fiction section. A well researched historical fiction that focuses primarily on the protagonist finding a love interest that not only reciprocates but is worth of her love will be put in the Romance section.
So, just because it's something else, like a Mystery or a Spy Thriller doesn't make it "not romance."
But I can't resist syaing this either: in your "You've Got Mail" example, the film will no more prepare someone to read a Romance set in a foreign setting/time than it will prepare one to read The Sword of Shannara.
The short answer then, is that they share a primary plot focus on falling in love, finding the right person to be in love with, etc, etc.