Apparently, the other differences between an American P1 and an American P2 are:
1. The background, as ipickee said.
2. The characters. P1 has Bebitchi/Babytchi, Marutchi, Tamatchi, Kuchitamatchi, Mametchi, Ginjirotchi, Masukutchi/Masktchi, Kuchipatchi, Nyorotchi, Tarakotchi and...