If we cut ALL spending except for interest payments on the debt, Defense, SS, Medicare and Medicaid we would still have a deficit.
All of the above and then some must be cut if we are serious about saving our country.
But the different items you listed are all for different purposes and are funded by different taxes. So take them one at a time. The two most popular are SS retirement benefits and medicare. They are still in the black and have special taxes that do go directly to a trust fund for payout. So for now, don’t mix this up with FICA tax revenue which funds the others. Cut the so-called discretionary spending to match revenue tax (other-than SS and medicare tax revenue) and its problem solved. Any federal government functions that have to be eliminated or downsized can easily be made the responsibilty of the states that want them. The economy will then take off like a rocket. Then, you can make the changes needed to put SS and medicare on an actuarily-sound basis. Voila!