College should not (though often is) be confused with trade schools.
As far as instructor demand is concerned, there seems to be ample demand, but the supply of new cannon fodder (most last about two years) way outstrips the demand.
There are several in the US. Fairleigh Dickinson and FSU had BA programs that included scuba instructor and the Florida Keys Community College has an AA program with scuba instructor training.
You might to look at this program, or something similar. Garrett College at Deep Creek Lake in MD, has an Adventure Sports Management program.
Garrett College - Western Maryland's Premier Community College
Not really a SCUBA program, but you could tie SCUBA into it, and get many more options.