Spending mostly consists of five things: Social Security, Medicare, Medicaid, defense, and interest on the debt. Everything else is relatively small.
These things are very difficult to cut. Medicaid probably has the least potent political constituency, but most attempt to cut it involve making the states pay more - which the states, of course, are against.
You are 100% correct. Of those, the one with the most room for actual cuts is Medicare, where huge sums of money are either wasted on harmful interventions, or spent treating patients with heroic measures, who are dead anyway 30 days later.
But when you try to address this in any way, you’re accused of creating “death panels” by the right, or “pushing granny off a cliff” by the left.