AI is low among the risks to humanity. Volcanism, WMD proliferation (nuclear war or the release of genetically engineered treatment resistant soviet era virulent pathogens, EMP attacks which destroy all power generatiing capabilities and electronics, pollution, mass extinctions, loss of arable land, overpopulation, and the exhaustion of remaining portable water supplies, climate change, destruction of rain forests and aboreal forests and the resulting bird, swine, bat derivative zoonotic pandemics present a far more immediate threat which could very easily surpass the tipping point and overwhelm our very limited capabilities to cope and adapt. Our healthcare delivery system barely works now and in times of real stress and pandemic induced fear, it would collapse as would much of societal order.
As a species with limited abilities for cooperation and long term vision and stewardship, we will be lucky to survive so long as to find civilization threatened by AI.
The remainder of this century may be worse than the preceding century in regard to global warfare, genocide and WMD proliferation and first use in wars for border, water and food security. Emerging pandemics could vector globally in days or weeks such that as possible causes of mass human deaths go, AI is very low on the risk scale for now and well into the future. To date, we have done an amazing job of irreversibly degrading the planet's ability to sustain the world's population without the assistance of AI, so I doubt the advent of AI would represent the tipping point for civilization. Like any technology, it can be wielded in any number of ways and there is no reason to assume that AI would come to view human kind as an infestation or plague in need of containment.
If you desire to be afraid, consider what would happen if a small nuclear device on board a cargo plane were dentonated at 35,000 feet above Omaha. How many days and weeks can our cities survive without power, transport, food, water or fuel all of which would cease to be available in a nanosecond due the resulting EMP which would fry all unhardened motherboards and circuits and black out the nation for years. 90 percent (270 million) Americans would perish. We do not need AI to extinguish civilization, but perhaps it could help save it.