Abraham Lincoln proclaimed a national day of fasting (http://www.abrahamlincolnonline.org/lincoln/speeches/fast.htm) because the nation had forgotten God and become too proud to rightly submit to Him. President Lincoln knew that refusal to submit to God results in punishment.
This is even more true today. We see clear evidence of major problems in our nation, including drought, economic instability, increasing aggression from enemy nations, and increasing violence within our own nation. We have rejected God's standards of living upon which our nation was founded - in particular God's family structure.
Therefore, we request the president to proclaim a national day of fasting and repentance so that we may genuinely humble ourselves before our Father.