*looks at topic*
There are various reasons why it happens.
The main one works like this, the American "philosophy" of learning a character and the Japanese philosophy. Yes, this concept exists. I quote American because it's not really an "established" idea, but it's more of an understood concept.
In America, when a person learns a character, more often then not they learn combos first. They learn big, huge *** flashy combos. Next, or maybe first depending on the game/character, they learn ways in which to win the fastest. In smash that'd translation to somebody picking up fox and learning how to u.air juggle and then shine spike.
In Japan, when a person learns a character, they learn to defend their character first. Plain and simple. They learn what moves work in what situations, how to move when nothing works (or it's to their advantage), and when and what they should block BEFORE they go off learning combos. They also learn how to effectively punish from their defense as well.
In short, you have offense vs defense.
Now the way it works, you can learn this an awesome combo all you want, but if you never find (or create) the opening to land the combo, it doesnt matter. On the other side, as long as you defend yourself and punish every mistake, it doesnt matter if you CAN combo or not, you know when you're guaranteed damage.
So because of that, more people can settle for having to wait for their opening to get their damage as opposed to wanting to just run in and destroy everything (Which is pretty much the difference of what you see between the countries, for the most part).
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You can also go into the easy/cookie cutter factor between the countries, and that's a real easy point.
Whenever you see fighting games played in america, they're usually played for money.
Whenever you see them played in japan, it's usually for pride/ranking. (Unless I'm misinformed, SBO (Super Battle Opera) is the ONLY japanese tourney that pays out).
So when most people in America play, they're going to want the easiest win possible because money is on the line. You can argue against it all you want but it's a fact. This makes them play the easiest characters possible. (Not specifically the best, but that's a game-by-game case).
Since the japanese dont have as much on the line, they're more inclined to play characters they like or ones that offer up more of a personal challenge as opposed to just mainstreaming everything.
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In short, you can say "Japan defies the tierlist", but there're reasons why. It's not like they're superhumans or anything. (Well, some of them atleast. XD)