You may very well be right, rcboater. As a matter of fact one of my earliest memories is of a plastic toy United States (considerably bigger than the Revell kit) that had a flat bottom and wheels to facilitate cruises around the living room.
It's also true, though, that in the early fifties the underwater hull lines of lots of WWII-vintage ships were still classified. The old Revell Missouri was a bit of a special case. The original, 1953 issue of it (Revell's very first ship kit - apart from the tiny Gowland sailing ships Revell had begun distributing a year earlier) had an electric motor. (My source about all this is, as usual, Dr. Thomas Graham's history of Revell.) In order to accommodate the motor, batteries, etc., the hull had to be pretty deep. Its depth probably is somewhere close to the scale - but in every other respect it bears little resemblance to reality.
What really seems weird is the inclusion of those "trestle" stands. What would have been wrong with telling the purchaser that the model was cut off at the waterline? (For that matter - what would have been wrong with cutting it off at the actual normal waterline? Several of those old kits - the T-2 tanker and the C-3 freighter, for instance, look improbably lightly loaded.)
Apparently, though, nobody minded the strange sight of a waterline model sitting on trestles. We did have different ideas about scale fidelity - and rationality - in those days....
Maybe the day will come when some company will give us a new, accurate United States kit. (There's no problem figuring out what she looks like below the waterline nowadays; the museum where I used to work has the original plating model - as well as a good set of plans.) The number of holes in the available lines of merchant ship kits is enormous, but a good model of the U.S. would plug one of the biggest ones. She was, in her brief heyday, an important and beautiful ship.
I saw her once when she was in active service - when my parents took me on a vacation trip to New York in (I think) 1966. I remember the cab driver explaining that she was immobilized at her pier because part of the crew was on strike. The significance of that didn't strike me at the time - but it marked the beginning of the end.
I also had the great good fortune to get a close look at her (or parts of her, at least) in 1982 or 1983. At that time she was tied up at Norfolk, Virginia, supposedly on the verge of being converted into a cruise ship. (That was one of many proposals that never came to fruition.) Much of her original equipment and decoration was about to be stripped from her, and the museum where I worked was trying to acquire it. So my boss and I got a guided tour of a lot of her interior spaces as we made up a shopping list. The museum eventually got, among other artifacts a spun-glass sculpture (called "Expressions of Freedom") that hung over the bar in the first-class dining room. (We had quite a fight over that one. A certain member of the museum's board of trustees tried to veto the purchase, on the grounds that "I've eaten many a meal under that thing and it's always made me want to vomit." Museum studies 101: whether you think an artifact is pretty or not is irrelevant. What matters is its historical significance.)
Some of the lesser items eventually were offered for sale in the museum gift shop; I got a nice little shot glass. My favorite souvenir of her, though, is a postcard that I picked up from a desk somewhere around the bridge. It has a picture of the ship on the front, and spaces on the back to fill in the departure and arrival dates for a particular Atlantic crossing; the cards were passed out to passengers as they disembarked. After considerable thought I worked up the nerve to ask our guide on that afternoon tour, Commodore Roy Alexanderson, to sign it for me - which he graciously did.
The last time I saw her she was tied up to a pier in Philadelphia, within sight of I-95. (We went through at rush hour; my wife was scared stiff that I was going to wreck the car because I was craning my neck around, looking at "one more d--n ship.") She looked pretty rusty and sad, but still, in a certain way, majestic. I do hope she comes to some end other than the scrapyard.
In any case, if a plastic or resin kit manufacturer ever does release a decent S.S. United States kit, I'll be at the head of the line to buy one.