Unfortunately, that's a huge issue right there. Right now, we have all our human eggs in one basket. I don't think enough people are aware of the somewhat long list of events that could knock people back to the stone age or farther. There ought to be a bigger push to branch out to other solar system bodies imo. Note I don't say any of these things is imminent or likely anytime soon, but they are inevitable, pretty much. The Tanguska meteor arrived from off the plane of the solar system so we had no warning of its approach. Imagine if it had been much bigger.
Edit: see if this isn't enough incentive, if Kim Jong Un set off a nuke in the upper atmosphere above North America, the resulting EMP could knock out electronics across the entire US.