I wouldn’t say that. Many American casseroles start with uncooked noodles, rice, or potatoes. Tuna noodle casserole starts with uncooked egg noodles. Chicken and rice casserole typically starts with uncooked chicken and rice. Funeral potatoes (yes, there is such a dish) often starts with uncooked potatoes.
You’re correct that most American casserole recipes came from magazines or boxes. They’re not fancy food. They’re usually made with cheap ingredients than can be thrown together quickly. A lot of casserole recipes call for things like canned cream of mushroom soup and crushed corn flakes.
A meat+veg stew with gravy, but cooked in the oven in an earthenware casserole, not on the stovetop (it is permitted to brown the meat there first though).
Things that disqualify most American hot dishes:
Starches like pasta or sliced potatoes as a major component, not root veg used as just one of the vegetables in the stew
Layers
Milk/cream-based sauce or else fairly dry
Top layer of cheese gratin or similar
Often in a shallow rectangular dish I’d call a lasagne dish, not a deep casserole.
The baking is the only thing they really have in common. But lots of other meat dishes are baked and aren’t casseroles: pies, lasagne, moussaka, meatloaf - so that’s not a distinguishing feature.
Lasagna isn’t usually called a casserole, but I would argue that it is one nonetheless. What Americans call “pie” isn’t a casserole, because it’s a dessert, and a casserole is a meal. On the other hand, shepherd’s pie is definitely an (American) casserole, and a pot pie is either a casserole or something very close to one. Coming at it from the other direction, a meatloaf also isn’t a casserole, because it’s not a full meal: Meatloaf will generally be served with side dishes.
If the same dish were made with other types of noodles (like fusilli) I think most Americans would consider it a casserole. I think the fact that lasagna is in its own category keeps people from thinking of it as a casserole.
I think that a large part of the reason that lasagna isn’t thought of as a casserole is because those noodles aren’t really used for anything else. I’d bet most Americans would categorize baked ziti as a casserole.
I was maybe eleven years old when I ran across it in Little Women.
Nobody’s mentioned haggis yet?
"Fair fa’ your honest, sonsie face,
Great Chieftain o’ the Puddin-race!
Aboon them a’ ye tak your place,
Painch, tripe, or thairm:
Weel are ye wordy of a grace
As lang ‘s my arm.’
– Robert Burns, “Address to a Haggis”
‘Good luck to your honest, happy face / great chieftain of the pudding race! / Above them all you take your place / Gut, stomach-lining or intestine / You’re well worth a grace / As long as my arm’.
By and large, in the US, haggis exists only as the butt of jokes (though I think it’s since been displaced in that role by hakarl). Most Americans have never tried it, and certainly no American would consider it a kind of “pudding”.
Any dish baked in pan, especially one containing multiple ingredients, is considered a casserole by somebody here in the US. Layered ingredients are often named ‘_____ casserole’. The contents can be anything from the consistency of a stew dished out with a spoon, to a dish that sets up and can be served in slices. There are dessert casseroles, both hot and cold. And of course vegetarian casseroles with no meat.
It seems the term casserole here in the U.S. of A. means food served in a casserole pan.
So the real question here (or some other thread) is “What is a casserole pan?”. We all know one when we see one. They may be square, rectangular, circular, or oval shaped, etc., but if a recipe specifies a casserole pan we know what will work.
Good one. Haggis is not only a pudding in the original sense of boudin, but Burns’ mention of the ‘pudding race’ is referring to a taxonomic or familial category of puddings.