The Trust Fund is a separate entity inside the government. SS has a set, specific revenue source, the payroll tax. The investment of the trust fund in federal securities is no more the government issuing IOU's to itself than is a soldier buying a savings bond.
Wrong. The soldier owns the savings bond, not the government. The SS Trust Fund is part of the government. What the government did is issue an I.O.U to itself. They are not a source of funds the government can draw on because the government is the entity that has to pay them off.
It takes a special kind of stupid not to understand how worthless the Trust Fund is, especially after having it explained as many times as I've explained it to you.
Here's an exercise in learning by doing. Take a piece of paper and write "I.O.U $2 trillion dollars." Now, stick it in your pocket. Are you any richer than before you wrote the I.O.U.?