Even though the concept of Jack-o-lanterns didn't come from America, I think a lot of people tab it as a kind of American tradition to carve pumpkins (at least from who I've talked to). I actually had the opportunity to carve a pumpkin with some Japanese friends, and none of them had ever done it before. We're also doing a kind of mock trick-or-treat for the Japanese children who live in my neighborhood tomorrow if the weather permits (crappy typhoon weather right now in Tokyo).
Here's a video of the pumpkin carving anyway.
YouTube - Japan Pumpkin Carving 2010