Most RAF bases have zero US presence.
Well, OK, I admit 'own' was an exaggeration.
My info is a few decades old, and half remembered. From a documentary about the overabundance of US bases worldwide.
My impression was the RAF let us take over during WW2, and we never gave it back.
The RAF let the USAAF and later USAF use (and/or build) large numbers of bases during WWII and the immediate affermath. Most of these bases reverted to the RAF or were closed during the late '40s and early '50s. There are abandoned airfields
everywhere in East Anglia and Lincolnshire, built between 1942 and 1944, to take advantage of the wide expanses of flat ground, close to the East Coast (and therefore close to Germany and Occupied Europe).
A few dozen were kept by the USAF for Cold War purposes; Most reverted to the RAF in the '90s.
Today there are ten USAF bases in the UK, some sharing runways and facilities with the RAF, and some routinely used only by the US.
The RAF Regiment (the ground combat arm of the RAF) are tasked to provide wartime perimeter security at these facilities; The MoD Police (who are not a part of the UK armed forces, and not to be confused with the Military Police, who are part of the Army) provide perimeter security in peacetime.
The relationship between the UK and US over these bases is very friendly; The US haven't been asked to give them back while they still wanted them, and the US have given back any they don't want, as and when they became redundant.
For example, US SAC had a base at Greenham Common during the Cold War, which was also the main RAF base for the UK's nuclear cruise missiles. The US withdrew their forces in 1991, and the base was closed in 1993 when the RAF also decided they no longer needed it. It was later used as a filming location for
The Force Awakens and
The Last Jedi, wherein the hardened Cruise Missile bunkers played the role of the D'Qar X-Wing base.
A friend of mine was driver of one of the cruise missile trucks based at GC in the '80s. They had a full scale training exercise, and the peace protestors blocked the gate to the base by lying in the road. As he had been ordered to act as though an incoming Soviet strike had been detected, and his role was to get the missile off base at all costs, he simply drove the truck through the perimeter fence, leaving a huge gap that the protestors used to invade the base.
He was cleared of any wrongdoing by the inquiry, though the MoD Plods were not so fortunate, as it was their job to keep the perimeter secure, whether or not an all terrain heavy missile launcher had just been driven through the fence.
