They'll never cut defense spending. That's where the most grift and corruption are, and that's the bread and butter for any politician to horse-trade for what they want.
I'm talking about the Trump administration. They ran on strong foreign policy, want to use the military to deport people, and are ramping up to deal with China.
If you take a look at the graph you linked you'll see for the years in Trump's first term (2017 through the end of the time sequence data in 2023) that it goes up (after starting 2017 down as a result of the previous year's budget) year on year, not down.