I agree that there is very little direct power. However, the President has a lot of power in picking the executives running various governmental departments. And staffing them with competent administrators and not political appointees is the most important way the President can influence decision making without actually having to make the day-to-day decisions. This is a pretty standard advice to middle and upper management. Obama failed miserably in this. Sibelius and Napolitano are classic examples of obvious incompetence, I'm sure you can name many more. On the other hand, Frieden appeared very competent... until last month. So there is that. And whoever advised Obama on how to deal with Snowden should never be allowed to advise again.