This a different Matt here, not the AMPOD.
I think Matt's "Mass death" is perhaps hinging on the possible fracturing of the food networks that we in the US have made ourselves so dependent on.  Losing one link in the chain will cripple big chunks of the works.  When the grid goes down in a city for even a day or two, tons of frozen food gets landfilled.  What if it tanks for a month?
Natural gas to residential users seems vulnerable.
Cross country trucking, same.
Fuel prices for agriculture...
I agree that none of these seems to be about to force a collapse altogether, but I envision typical Americans being unable to cope if they lose their access to frozen pizza and the juice to run thier microwaves and keep the diet coke cold.  
We had an extended blackout here in DC after a bad storm 3 years ago--not the big northeast blackout--and people were utterly helpless.  We modern Americans have essentially no skills to function if any one of our technological lifelines is cut.  
So, I wonder, how long before people panic if they can't: drive their car, cook their food, buy food, take a shower, heat their home.  Just one of these things breaking down will freak people out in a major way.  
Not "mass death" right away, but the beginning of a growth curve of panic driven crime committed by people who would never have called themselves criminals in the current paradigm.  Unprecedented anxiety that seems unresolvable will trigger a lot of bad behavior.
-Matt, DC