“1. Roll the US Marine Corps into the US Army. All ground forces should be in the US Army.
2. All airplanes should be in the USAF.
3. All ships should be in the US Navy.”
#1 - agree
#3 - agree - roll the Coast Guard into the Navy
#2 - disband the USAF and repurpose it to the Space force.
The reason is that the air support mission for the Army and Navy differ quite a bit. Army planes don’t need to land on carriers and Navy planes are not suited to ground support missions (generally). The DoD has to spec out two different design extensions when ordering aircraft - very expensive.
Air support missions can’t be made without gaining air supremacy. The Soviets found this out against Germany, and we did, too by trying to push just bombers over their territory.
You have to sweep the skies of enemy fighters before you can use aircraft as flying artillery. Otherwise your flying tanks all auger in.