When I worked for a defence contractor the Troubles were still a thing, so on the British base there'd be a chicane and armed gate guards, no crashing through the gates and blowing stuff up inside the base for you. But at the US airbase there was just a sign saying Condition Black (ie no danger) and you could walk in, presumably the terrorists weren't dumb enough to attack a bunch of American school kids whose parents were military given that a lot of their funding came from America...
Ostensibly the reason I'd be visiting that US airbase was vital urgent paperwork being transported personally by a British officer, who was entitled to the use of a vehicle which I was driving, to some senior American personnel - but we sure did seem to generate a lot of such paperwork and we always bought back donuts (which the Americans have on their airbase) ...
Anyway, that US airbase is definitely not American soil. I did actually own a passport, and I had the right to enter the US, but I was never asked about it because the airbase was in Britain, on British land, merely on loan to the Americans indefinitely.
This is not the same thing as maintaining sovereignty. The US has bases in many countries, but it's not native US soil