The Outline of the Federal Government

Instead of looking at what to get rid of, lets look at what is absolutely needed and allowed for under the Constitution.

Department of Defense
Department of Justice
State Department
Treasury Department
Federal Courts System
Patent & Trademark Office
Department of Federal Transportation services and maintenance
Department of Veterans Affairs

National Archives, Records and Historical works
Internal Revenue Service, to include Tarriff Gathering (although the entire thing becomes tiny)
Census Bureau
Bureau of Industry and Security
International Trade Administration
National Oceanic and Atmospheric Administration
National Technical Information Service to inclue Telecommunication Services
National Weather Service
US Forest Service
Nuclear Regulatory Service to oversee all aspects of Nuclear use within the US, including detection and preparedness
Food and Drug Administration, to oversee guidelines, standards and inspection of same
Drug and medication testing and standardization service for all drugs and medications
National Institutes of Health
Centers for Disease Control
Federal Health System, with oversight and regularization from NIH
Administration for Native Americans for those roles not coverd by the State Department
Immigration, Naturalization, Border Control, Customs, Inspection and Enforcement service
Federal Emergency Response Management Agency with the current CERT
US Secret Service for protection of the Federal Government Elected Officials and Supreme Court
Office of Disability and Catastrophic care for Citizens
Office of Engineering Design Best Practices (currently parts of OSHA and Mining safety, oversight, reclamation and health)
Veterans Health, Employment, Disabilities and Safety Bureau to be included with DVA
Bureau of Land Management
US Geological Survey
National Park Service

Do note that the Intelligence Community needs reform for the modern age. I have posted on that elsewhere.

See anything missing that is to "establish Justice, insure domestic Tranquility, provide for the common defense, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity" ?

As to why so much is missing... well the Policy section should take care of that!