The short version: the President takes an oath to uphold the Constitution. The
Fourteenth Amendment, Section 4, says that "The validity of the public debt of the United States, authorized by law,...shall not be questioned."
By implying that Social Security faces a crisis in 2018, when a crisis could only arise by the United States welshing on its debt to the Social Security Trust Fund, Bush is questioning the validity of that debt, contrary to the Constitution he has sworn to uphold.
Since Aragorn can't summon his shade to the Stone of Erech, I think demanding the impeachment of the oathbreaker is the best alternative.
After all, if lying under oath about a blowjob was a sufficient ground for impeachment, lying in the oath itself about something important surely qualifies too.
In addition, every member of Congress and every Executive Branch official takes a similar oath. (Presidential, veep, and Congressional oaths at this GPO page; this Treasury page says all Executive Branch officials take the same oath as Congresspersons.)
I bet there are a lot of GOP oathbreakers out there.