I largely agree about the major in the USA. I disagree though that the study of what can be computed is anything other than a discipline of mathematics. Computing science itself never requires stepping outside discrete mathematics, which of course means the majority of math just isn’t necessary to do theoretical work or write correct programs. But then what mathematician today has mastered the entire field? It’s too big, you have to focus.

However, there’s considerably more to it than that. With a few rare exceptions, the overwhelming majority of CS programs in the USA are “telescope science” and not astronomy. One of the more telling, and to my mind obnoxious, evidences of this is how even in the academy the CS types literally appear to believe that “formal” means machine checkable while at the same time balking at learning basic first order predicate calculus to actually specify what is to be computer by a given program. Clearly they are studying the machine and not the mathematical sub-discipline.

I emphasize the USA, because having done many many FAANG technical interviews there is a discernible pattern of graduates from continental European CS programs being considerably more mathematically literate.