The leaders of the New Atheist movement are not heroes; they are certainly imperfect. I agree with all of your criticisms, but you say nothing of the bulk of their work.
Hitchens’ God is Not Great will stand the test of time; his Islamophobia will not.
Dawkins’ The God Delusion is still correct, despite his late-in-life transphobia and “cultural Christianity”.





Worst case scenario is Venusification, where runaway climate change forces make earth literally uninhabitable for all known lifeforms. If we continue on our current path this is a likely outcome.
Your less-apocalyptic scenario is one where our global economy collapses. If this happens, no area of the earth will be safe. Food production will drop by 80-90%, which means that human population will have to drop by 80-90%.
Your assumption that the West will be a safe haven is incorrect. The West’s economic advantage relies on imports, and in a collapse scenario those imports will stop. We can see a small version of this during the current Hormuz crisis- without middle east oil, weatern farmers have limited access to fertilizer, therefore crop yields are down significantly. Without fertilizer imports, the West cannot farm. Without natural gas imports, the West cannot heat its buildings.
In the collapse scenario, the violence won’t be localized in places like the US border. Humans, even in western nations, will be desperate. Your neighbors will be watching their children starve to death. They will be willing to break down your door and beat you to death if you have food.