What about....
supervolcanoes? Ever think about the effects of Yellowstone on a global financial scale? We would no longer be able to to use our troops (both U.S. and Canadain) overseas. There would be too many rescue missions here at home. Crops threwout the U.S. would be effected due to the ash cloulds and weather change (dropping around 10 to 20 degrees here in the U.S.). Those that servive would turn either primal or religiuos. Both could be a deadly and dangerous mix. Gangs would rome the empty cold streets looking for food while others would be gaurding their own food. Not to mention the fact that even outside of the (killzone) nuclear winter may happen as well. nuclear plants in that area would either shut down or turn into three mile island(s) all over again...
Just something to sleep on. But places without our support and help (Africa, middleeast, Asia and Asia-minor) would not have the support of our troops, medics, nor would they be able to provide much help to us. Consider this, most planes can not fly over volcanoes due to the ash clouds. That would stop a lot of much needed medical supplies and aid to our on country and others. It would not be just a U.S. thing but a world thing.
Over just a couple of years the weather would create a (new) ice age in some regions. Creating storms we have never seen ACROSS the globe.
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