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Richard65 Never underestimate the enemy.
The USA is not the only world superpower. There are two: the USA and China, and China is after being Number One, and probably on course to be that.
She has the advantage over democratic nations of being a stable dictatorship able to plan years ahead without worrying about the uncertain twists and turns of multi-party electoral systems and public opinions.
The Royal Air Force bases in Britain are RAF (i.e. the property of Great Britain) albeit that some are used by the USAAF. The USA also has an enormous radar and radio listening-post in the North of England, and that is America's though I don't know the land-use arrangement.
Of course they are secret! All military bases around the world hold their secrets, so the description as "top-secret" is superfluous.
What was frightening is that at the height of the Cold War, America plonked nuclear-armed ballistic-missiles on the British Isles with no plan to ask the UK government permission to launch them. So a foreign country would be more likely a prime target than the USA, at least in theory.
(Both countries would have been targets of course, and no amount of playing tortoises under school desks would have prevented vast losses of life to all warring nations.)