We are going to have to agree to disagree on this one. I'll defer to you on whether the Ron/Hermoine and Harry/Ginny relationships make sense in the books. But they didn't make sense to me in the movies. All the "fights" they had seemed very forced and just another version of the trope that when girls and boys like each other the boys are mean to the girls an they both secretly like each other. There just wasn't any real chemistry between Ron and Hermoine in the movies, or between Harry and Ginny for that matter.
As far as it being an "Americanized" view, I think it's the opposite. I think the Americanized view of these things is that the nerdy guy ends up with the hot girl who realizes that he treats her better than the captain of the football team who is as arse. Harry is not American and despite being captain of the Quiditch team, is not an arse. So it's not at all an American point of view. In fact, it's the opposite of what Americans expect for the nerdy girl to end up with the captain of the football team. Captains of football teams end up with the popular girls, the cheerleaders and Ginny arguably fits that role more than Hermoine.
Anyway, to me the movies very much so made it feel like Harry ended up with Ginny as a second choice and the fact that Harry and Hermoine wanted to be more than friends seemed very clear to me in the scene where they danced to the Nick Cave and the Bad Seeds song in the tent.
Maybe it's just bad film making that does not reflect the books, but I don't see those relationships as working in the movies. Doesn't ruin the movies but I did find the ending very odd and sad in that regard.