Many folks cannot understand how we came to have such a severe oil shortage problem in the "Land of Plenty".  Well, there's a very simple supply and demand answer. 
     Few people have the mechanical knowledge of where the oil is located.  Once they discovered it was getting low, it was too late.
     The reason for that is purely geographical.  United States oil is in Texas, Oklahoma, Alaska, etc., but all the dipsticks are in Washington, D.C.