There is no room for fat in the services, all have an essential role. The fat is the procurement of equipment to do the work. We are working on keeping cost down but it is out of control the private contractor is fueling much of the pork. 60 Minutes had a segment on the doubling cost of fighter jets. They have problems and when they do we were paying to fix them. It is the way of most procurement, if the government needs it business bids high and until recent past have had issues.
The value of each branch being equal we can not cut even a little bit. The Marines are the the first response The navy gets them close and supports the effort. The army mopps up and maintains the ground we get. The air force air dominance and surveillance pinpoints targets. The coast guard first and last line of ocean defense plus the save lives of people that have problems. They track and monitor coastline traffic for criminals.
We need them all and depending on the situation one will always stand out.