Clannad is a universal story. I don't understand why it wouldn't be successful as a Hollywood film.
In fact there was a movie "
Love Story" in 1970 that was a huge hit and dealt with very similar themes. It's the source of the quote: "Love means never having to say you're sorry."
Of course, being a melodrama means there will be haters, but there are plenty of movies that made tons of money despite not being universally popular. Twilight for example.