Utada, while fantastic in her Japanese releases, released extremely mediocre material here that would never stand out on our airwaves. She views Japanese and American audiences differently, and yeah while they do generally have different tastes (she even said Japanese care more for good lyrics), her stuff here is still a letdown even with big name producers.
Hmmmm... I think Valenti was a song I had. And Rock With You. To be honest I never heard BoA's Korean stuff but I have heard she puts more effort there. I remember now that her JP stuff was too sugary for me (and so was some Ayu.... Also why I never got into Morning Musume.)
Fun fact: I used to confuse her with Boa, the British one who did the awesome Serial Experiments Lain theme.