WHAT HAPPENS WHEN "IT ALL GOES DOWN"?

I want to start this thread as a place for realistic discussion and suggestions for what a survival scenario might look like if it "all goes down".

Imagine what might happen if we go into a full-scale world war. The power grid goes down, enemy countries invade the united states. We are already in mass chaos from no power, loss of water and food supplies and possibly worse.

What do we do?

Where do we go?

Where do we find food?

How do we know who to trust?

How do we survive a scenario like this?