While there can be noticeable gaps between JP best and everybody else's best, I'll add people who think the JP possess some god gene that allows them to rule fighting games to my peeve list.
Biggest , and most obvious, difference between JP and the rest is the arcade scene. Any country that could, or would, replicate the number or large and vibrant arcades they have would inevitably replicate the skill in players.
Dispite their skill, the impression I've gotten from the JP is they just don't take the games as seriously as most others I could name. When they lose they don't get salty, they don't ragequit, they don't insult the winner. They just say " oh well, I can do better next time" and keep playing.
I'd also add that winning these tounaments doesn't necessarily make you the best, just the best of who showed up.