That money is included (and spent-badly for the most part) in the general operating budget of The United States (Thank you yet again, Lyndon Baines Johnson).
"The Social Security Trust Fund" is a sham created to lull the jejeune and the uninformed; it consists of U.S. Govt. I.O.U's backd up by nothing.
Congress has waited twenty-five years too long to get this problem under control. What will happen eventually are unpalitable "solutions", e.g., means testing, benefits reduction, tax increases, and a dramatic upward push on the retirement age. All of this still will probably not be enough, which will tempt future governments to inflate the heck out of the economy in order to pay benefits with cheap dollars. This will destroy savings and investments of course but the Socialists will get another excuse for more government control.
If you would rummage around a bit for the facts rather than just drinking the Kool Aid (Jonestown Grape seems to be your favored tipple), you would not make the promouncements that you do.
And how far could you or I get at the bank keeping books like that?........Not many folks recall LBJ covering his a$$ ( and DEM spending) by combining the 'budgets.'