Is it a good idea to introduce myself via email after submitting application?
I think that in most US places, such a letter is likely to be ignored. The application itself should be used to show such strengths, perhaps in a personal statement. But a university with a large number of applicants has fairly strict rules about addenda to applications. I doubt that it would improve the chances, but would, most likely, not harm the case, though it might if he seems desperate.