At least some classified stuff is well known to other country's intelligence services, friend, neutral, and foe. It can be so far out of the bag, it's had kittens.
Lot of stuff is classified not because it would actually prevent other nations from finding out stuff, but to hide from the American people and press embarrassing things like how much money is being spent on that particular project or weapons system, how much of a failure it has been, how much toxic waste is being created in its manufacture, and so on.
There's also all the stuff Internet Armchair Intelligence Officers think is "sensitive" or "classified."
Lot of stuff is classified not because it would actually prevent other nations from finding out stuff, but to hide from the American people and press embarrassing things like how much money is being spent on that particular project or weapons system, how much of a failure it has been, how much toxic waste is being created in its manufacture, and so on.
There's also all the stuff Internet Armchair Intelligence Officers think is "sensitive" or "classified."