1955 Map Shows No-Go Zones for Soviet Travelers in the U.S.

One thing that jumped out - "Travel restrictions on Soviet private citizens stayed in place, enforced by the Departments of State and Justice, until the Kennedy administration unilaterally lifted them in 1962 as a symbol of the openness of American society."

The administrations in question were surely perfectly aware that there was no such thing as 'Soviet private citizens' just up and traveling to the US.

But, anecdotally at least, the symbolism did work - my father first visited the US in the early 70s as a Soviet-bloc citizen working for UN IAEA Safeguards. He was impressed by how unrestricted his travel was - he wanted to extend his trip slightly to do a bit of sightseeing - the Grand Canyon and Vegas (I think both off this map). His hosts helped arrange it for him in a few minutes and with a couple of calls. To a travel agent, not the CIA.

Which may seem innocuous now but it was the height of the cold war, the UN was a much-beloved Soviet spy-insertion vector and the working destination of his trip was, in fact, Oak Ridge - not a place famous for its guided tours.

Lots of nuclear sites, all with very wide swaths of coverage - Hanford, Savannah River, big chunk of New Mexico and surroundings, Nevada. I'm guessing places in Colorado and the Dakotas that a little later became various bits of SAC/NORAD/etc were already homes to sensitive Air Force bases and related facilities.