Safest place?

I don't think there is one.

Natural disasters don't care. Storms and tornadoes can pop up anywhere. Long dead fault lines can become active. As I understand it much of Kentucky is waiting for a Big One that will surely come and level the area sometime between now and the end of time. The Sierra Nevada is waiting for their own spectacular regional Big One.

I don't believe in these sorts of things but they aren't entirely impossible so they remain something to throw into the mix. If the "Nemesis" hypothesis, or one of its many variations, a large asteroid of some description aimed at earth, is correct or the claims of a cosmic 'death beam', an X-ray jet from a black hole which will be aimed at us soon, are true it really doesn't matter where you are everyone dies. If your on earth your pretty much screwed. I suppose if your lucky your near the epicenter and die quickly. The advice to "Embrace the horror" (preferably with chips, dip and your drink of choice in hand as you kick back in your lawn chair and watch the show)is about as good as any I guess.

Anywhere there are humans your risking random violence, jealous rage from jilted lovers, imported disease (children are little disease incubators and distributors), terrorism follows population concentrations as do economic collapses and riot.

Of course if you wishing to avoid untimely death on a more personal level, a far bigger risk than a nuke, avoid motor vehicles, exercise regularly and eat less meat. It still won't help if you slip in the tub and brain yourself on a nice bit of chrome but life is inherently dangerous. Nobody gets out of here alive.

You can specify any particular risk and find an area that is relatively immune to that risk but there is, IMHO, too much overlap between risks. In the end I think the best you can do is pick your poison and take your chances.