People who answer survey questions seem to consistently display a pessimism bias about these large scale trends, and the equity premium puzzle also can be interpreted as people being unreasonably pessimistic about such things. So I find it hard to believe that people tend to be too optimistic about such things. If you really want to bet on the low tail of the global distribution, I guess you should listen to survivalists. If you think the US will be more down, why invest in foreign places you don't think will be so down.