It's a little surprising that Stewart would take such a watered-down job, but maybe he's (a) eager to get out of very low-spending Philly and/or (b) he has hope that the job will expand over time. For now, Stewart's job description will mostly be to give a managerial recommendation to the USSF board, then micromanage the manager.
Stewart's start date is August 1, which is worryingly late. If that's just when the managerial search process will begin, the US will probably miss out on some foreign talent that will be hired away earlier in the summer. If the search doesn't begin in earnest until that time, I'd say that increases the likelihood of an American (or at least MLS) manager.
I've read that Stewart is very tight with Gregg Berhalter. Berhalter is near the top of the list of American candidates anyway, so I guess it wouldn't be shocking if he turns out to be the pick. One problem with that hypothetical is that Gregg's brother Jay is probably the most powerful USSF official that nobody's ever heard of, so then we'd have years of acrimony about nepotism and lack of accountability, etc. Some of it will be legitimate, most of it will be axe-grinding, all of it would be extremely tedious.
Of course, I'm making a lot of assumptions in that hypothetical.