Well, finding Japanese stuff in Alaska makes sense since from what I can tell that’s where the warm northbound Japanese Current ends up and also where it turns to become the cold southbound Alaskan current.
True. But there’s two currents to consider: water and air. How an object is affected by them is a matter of size and shape. Some tsunami debris were found in California, and I don’t think they all made their way to AK, before heading south.