There's two sides to my opinion.

On one side, I am a libertarian. Federal government is to protect our county from foreign attacks, secure our border from interlopers, settle disputes between the states, regulate commerce across the borders, and... well.. that's all I can think of. Everything else should be left to the states. And only if 49 states agree something is better left handled by the federal government, should it be so. (There can always be one abstainer overruled)

On the other side, that will never get us to Mars, which I see as the most important thing we as a species should be doing right now. With that in mind, if we are to put that on the federal government (even if 49 states do not agree) then there's a bunch of other stuff that they should be responsible for. Namely public health, environmental health, education, regulating commerce inside the states, setting up roads (outside of strict military needs) regulating energy... but morality should always be left to the states.... in just about every way you could describe it... as well as respectively law enforcement. You would still have ICE and Border Patrol, but many of the branches of federal law enforcement should cease to exist.