could any of the kingdoms at middle earth attack the southern continents?

[Inziladun]

Originally Posted by Nerwen

That, I believe, is the sense in which "treating it like a game" is meant- the OP seems to take it as a given that world domination (more-or-less) is everyone's sole objective, regardless of practicalities.

Regardless of feasibility, as well. Gondor was quite incapable of launching an offensive against Rhûn or Harad with the aim of empire. As was seen, it was all Gondor could do to defend themselves from attacks by those enemies.