The .375 H&H is used in North America, but I would NOT call it a "North American" caliber. It was specifically developed for use in Africa, where it gained a fine reputation, and only later applied to select game animals in NA, such as the great bears. It is excellent for those too, but is OVERKILL on every other animal in NA! But, that does jnot mean it can't be used, and actually, a .375 H&H with a tough 270 or 300-grain bullet will ruin less venison than a .270, if you decide to use it for deer and elk, etc.

I am not aware of it being UNDER-RATED for any use anywhere.

BTW, the .375 H&H can be considered a "medium size" case for that large a bore size. It is NOT too well suited for use with the new slow powders, it doesn't hold enough of them. IMR 4350 and WW760/H414 are about the slowest powders you can use efficiently in the .375 H&H, and IMR 4064 (and any other powder with a burning rate close to this) has about the best burning rate for it.