You can do some historical research on this to find out how accurate it is.
As a refrence it was understood during and around the first century that each nation had some sort of spirit governing or ruling over it, evil or otherwise. The Creator being the one who was over Israel. First century gentiles believers, especially major head figures went to Hebrews for clarification on scriptures even after the Church was formed so they still had authority.
I'm assuming this verse presents two problems for WT. It interferes with their teaching that the Son is not a God, and it also can be said that Israelites of blood decendants are his portion, so it would destroy their "JWs are the new chosen" doctrine. It simply has to go, though they have other verses they left in (probably being too stupid to understand them) that illustrate the points I brought up better.