"Wintermas" is supposed to the the secular substitute to Christmas. However, the -mas comes from Mass, a religious term, and while it would be winter in the northern hemisphere, it would be summer in the southern hemisphere.
Where are the other religious groups? Where are the Jews, the Muslims, the Hindus, the various pagans, and who knows what else?
Reflective of the author's complete inability to understand anyone actually believes in any (version of) god than his specific variety of Christian one, and isn't just non-Christian out of some need to rebel. It came up in Left Behind as well, that everyone not Real True Christian was happy to abandon their religion as soon as the evil world government told them to.
How does the global atheocracy keep religious faith illegal and make it shrink into obscurity? Think about it. Muslim terrorist groups in the Middle East would lay down their arms and submit. Neglecting that factor, they probably assume Christians wouldn't fight back: which isn't realistic either. Plutarcho Calles attempted to outlaw Christianity in Mexico in the 1920's and that spawned the Cristero War.
Addressing both points above: Given that even the author doesn't seem to disagree with WWIII being caused by religions (Other than his, of course), perhaps many of the other religions had their populations sufficiently reduced during the war to make their removal relatively simple? It would fit with the series' tone and general dismissiveness of other faiths after all.
Since Earth is still a global democracy by the end of the book, the effective Gendercide at the end of the book would leave women in charge, which this troper suspects was not intended by Jenkins. The interim world president after the one from the first book dies is a woman.
Creating a desiccation zone in central Los Angeles, in addition to causing the death of thousands of people, would allow Atheistopia to benefit from near-free energy in vast quantities by use of type-two perpetual motion machines, as well as allowing any number of interesting chemical processes that would advance materials science by centuries.
An easy example: Have a canal that goes from the Pacific into the dessiccation zone. The water at the end of the canal will disappear, making room for more, thus generating flow in the canal. You can build a water wheel to harness that energy. Add airtightness to this (which would be trivial for people in the late 1800s, never mind the late 2030s) and you can generate a lot of energy with very little water (Also, what sea level rise?). On top of that, if not only the H20 molecules disappear, but the heat that they carry also does, you can basically make a type-two perpetual motion machine that only uses up a bit of water as coolant, since it's a theoretically perfect coolant. Here's a mini fic about it: http://emlia.org/pmwiki/pub/web/Tripocalypse.SoonSilencedInterlude.html
At the end of the second book, the "good guys" pray to God for a repeat of the slaughter of the firstborn out of the Old Testament, and the beginning of the third book indicates it's worldwide, not just targeting agents of the "evil" atheist government. Given how well the world is supposed to be doing, and known demographic trends - to wit, that as populations grow more affluent, they tend to have fewer children, for a variety of reasons - then it's very likely Paul and his cult just nearly committed a full-on Gendercide.
