No, that guy wasn't japanese. He's from Pakistan and he's an asshole.
And yeah, did suffer reverse-culture shock... mexicans seem so fucking loud and impolite now! I miss japanese politeness at stores, for instace, yesteday I was made wait like 10 minutes while they got my change. When I finally got it, it was almost thrown to me and the cashier was like "Ok, you got it, can you move outta the way?". If it was Japan they would've been all "::Bow:: We're sorry!! ::bow:: We've made you wait, here's your change. We hope you come again. ::Bow::"
Yeah, and some other things I miss....