The only resemblance I can really find in any music/songwise (they don't sample those artists music though, just a little simillar in their styles) would be:
Yaida Hitomi (listen to "Mikansei No MELODY") and Alanis Morisette (Listen to "Hand In My Pocket"), since they really play their voices to a certain tone and have songs that sort of slightly resemble a mix of country + rock + pop
Mikansei No MELODY:
http://youtube.com/watch?v=ICUKtw0F4Y0
HAND IN MY POCKET:
http://youtube.com/watch?v=nLXULfN77TQ
And to some interesting extent:
Nana Katase (Listen to "TELEPATHY") and Kylie Minogue (listen to "Can't Get You Out Of My Head") with their electronic pop:
TELEPATHY :
http://youtube.com/watch?v=LEUA9dxlHC0
Can't Get You Out Of My Head:
http://youtube.com/watch?v=5uxjNEESomA
Oh, and Tommy Heavenly6 (Listen to "Ready?") and Avril Lavigne (Listen to Sk8er boi)!!
Ready? :
http://youtube.com/watch?v=RA2NS2-pjxI
Sk8er Boi :
http://youtube.com/watch?v=pULa7F1gWZM