America split into western and eastern halves
It was thought that the war would be over quickly: "the rationality of humans won't allow this war to continue". However, the war did not end, and will never end unless one side gained an absolute initiative.
In this war of love and hate between men and women, both sides came to the same conclusion: "we're better off if we just didn't meet for now", and so the division began.
The western half is the men's country: The Orthodox United States of America
The eastern half is the women's country: The Free American Republic of Magic