Come to think of it. There is almost no Japanese fanart of ATLA or Korra.
Definitely untrue, especially with the way Nick kept screwing with it.
I think he meant "in Japan".
In America, Korra started out with AtLA's typical ratings, but for whatever reasons the ratings dropped and dropped and dropped, until it was kicked off the air and the end of the series was made available on the internet for whoever was left.
In Japan, AtLA's dub was bad and they may have disliked the "Fire Nation as Imperial Japan" metaphor, so AtLA was cancelled partway into season 2. As a result, the sequel Korra might actually be more popular in Japan than the original AtLA was.