Mainframe, MVS and zOS Discussion

Am I understanding it correctly? Apart from Mainframes, different processor architectures do fancy things with 1's and 0's that are pretty complex so they present an API of sorts which consist of the assembly instructions which can be used more easily that trying to directly manipulate the transistors on the chip ?

If you regard all computer languages as APIs, then you could regard Assembly-languages as APIs.

hmm...ok.

Computer languages would not typically be considered APIs since an application programming interface provides a set of calls / commands to allow use of an application. While a computer language is in a broad sense an API, more usually an API would be invoked through a computer language.