I'd like to shrink A LOT of it, including the DoD budget but also have Medicare and SSI be opt-in/opt-out and gradually fade them out. That said, our preamble outlines that the purpose (original intent) of the federal government is to promote the General Welfare and provide for the national defense, so Constitutionally, having the budget for a sufficient military is one of the core purposes of the federal government, as well as arbitration between states. Now, I am aware the language changes in Article I Section 8, which also states "provide for the General Welfare" which of course will be debated ad nausem until we can have an amendment to specifically define, clearly, what that exactly means. So there's a contradiction in verbs within our Constitution. Anti-federalists such as myself will clearly side with the Preamble language whereas the federalists will side with Article I. So we're at an impasse.
The bottomline is that the welfare state, created by FDR's New Deal has shown to keep the poor in poverty while massively funding military operations, black budgets, and handing out tax dollars to large corporations under the guise of "providing for the General Welfare" but it's nothing more than legal bribery and quid pro quo.
We wouldn't care so much about who the President was if the office didn't wield such immense power. I just want us back to pre-New Deal days economically.