I actually liked a theory Aohige had (I don't know if serious or not-so-much); seeing that Wanokuni is One Piece's Japan, and Kanokuni is OP's China, their countries could be enemies, just like in real life (just recently there was all that conflict over a stupid microscopic island)
That's Korea and Japan you goof. But the point still stands, I wonder if Oda is setting up some sort of relationship between Kano and Wano. It IS a good opportunity to introduce characters from the country (such as through the tournament) as a preface before they get to Wano.