Well... This world could be logical. I mean the men went extincts about 90 years before this point of the story. With the technology from pre-world war, medicine should be able to create artificial babies using female genetics (cloning to be more accurate).
Humanity has been priorizine one thing above all; survival. I am sure such thing as fund or hardship would not stop them. Plus, I read somewhere women were people of heart, full of emotion and capable of doing anything for their beloved children.
Even if it took them 30 years to develop that ips technology, it wouldn't be enough to have them extinct. Sure, some countries might disappear but that wasn't mentioned in the manga. Also, as the environment the female being are living in has changed, I am pretty sure they have evolved and most likely will evolve further as to adapt into their new world. It might take centuries or millennium. Who knows.
I personally love this kind of settling where one gender is totally whipped from Earth. I would like to see one manga with this settling but focusing more on politics, affair and military domains. Something à la Code Geass for example.
Anyway, I can't wait to see where this story will lead us to.