User blog comment:Chix777/Golden Darkness' Second Arc!/@comment-26576038-20150627162411/@comment-1875854-20150627163512

Konoha was the only place with BZ influence so Sunagakure doesn't have BZ in their walls or anywhere around. Further out though is a battlezone (the rest of the Land of Wind) that Black Zetsu is known to control.

And once the Shinobi Union is formed, we will essentially be invading Konoha to stop what Black Zetsu is doing there (after our spies find out what is happening).