The world will continue to go on, just as it did when Babylon fell, and when Rome fell, and when the sun set upon the British Empire.  The economic collapse of America is not the end of the world, nor the end of America. America will still exist, but in a much less free form. Just as the economic collapse of the Weimar Republic paved the way for Hitler's rise in Germany, America's financial decline will lead to a more totalitarian regime.

Therefore, one of the most important things you can do, practically, is get your financial house in order.  Think about making large donations to ministries that are actively fulfilling the Great Commission. 

Learn to grow food and have a plan for moving to a more remote area than you now live in. If you live in the city, have a plan for a move to a rural suburb.  If you are in a suburb, have a plan for moving to the country.  If you are in the country, have a plan for a move to a more remote area.

Get together regularly with a group of believers you love and trust and can be in local fellowship with.  A support group is very critical at a time of great change and uncertainty.  I have noticed that birds flock together before a large storm.  This is an instinct that apparently is divine. If you are in the Chicago area, contact me about the support group I am with.