You understand, of course, that the actor is not the character. The analogy here is obviously to the character who had big mommy issues, Ma Jarrett's little boy, not to James Cagney, actor. [You may be surprised to know that Cagney did not write Yankee Doodle Dandy.] ;^)
Actually I know he did not write it or he would have been about 200 years old when he did the role in the movie!!
White Heat is one of my all time favorite movies. The lines in it were memorable such as: she is wearing out the mattress a reference to the part played by Virginia Mayo; another where in Cagney says to an underling about using the radio: if that battery is dead, it will have company and lastly when “Parker” asks to be let out of the car trunk for more air and then Cagney blasts it full of holes!!