In most instances that is up to each state, not the president or Congress.
You and I both know that Congress today would never vote themselves out of pension. But if we get the right people in there, and if term limits were imposed, they may agree to demolish pension if their salaries were adequate.
pensions paid at the local and state level come out of local and state budgets... when there is a short fall, the fedgov picks up the tab
cutting the amount spent at the fed level means looking into why the fed is sending any money to the state & local govts
which will lead you to... all those pensions being paid to people that have never risked their lives for the country. (life guards, toll booth operators, town hall secretaries, etc)