Now guys, gon's obviously trolling. He doesn't really believe all japanese people are incapable of playing a card game. That'd make him a bigot.
But as to the question of why their champion sucked so hard in the last championship... Well, I wasn't around to watch it, but I'm not surprised that major suck-age occurred on his end.
For one, from what I'm understanding, their champion doesn't have any motivation to do well in this tournament. He was being asked to play what is essentially the same card game for him, but with a drastically smaller and different card pool without any reward of any kind. Add to that the fact that the japanese champ is going to play against players who don't even speak his primary language (or what may be the only language he knows), and you have a recipe for an event anyone in his position wouldn't really care about.
From what I understand, they also have a much larger card pool, and even the older cards are completely different from the US variations at this point. That's why their champ has to take time to acclimate to this new card pool and meta (which is a process that I would hardly care about as it doesn't seem all that fun). Their meta also probably looks rather different from ours, and judging from the few alteil 2 cards I've seen their cards tend to be more powerful on average.
So you gotta ask yourself: if you were to be asked to take your own time to practice and play an older, worse version of a game you play, against people you can't even talk to without any reward of any kind, would you be up for the task? You probably wouldn't really care either.
Oh but wait, how could I forget? National pride is on the line! That throws everything I just said out the window. Go! Win a relatively unknown online card game! Win for your country!