I'm in a similar spot.
I got in to Elliott School's International Affairs early last week.
I heard back from American just yesterday saying I was waitlisted for their International Affairs program.
I didn't get funding for either.
I called GWU fir funding opportunities and they directed me to their Office of graduate Student Assistantships and Fellowships http://www.gwu.edu/~fellows
I looked through, most of the fellowship deadlines have already passed. There are still some you could apply for (just check for eligibility). Also, I learned that only PhD students can do Teaching Assistantships.
I haven't checked out American's other funding sources yet. On a side note, since I was wait-listed at American, should I go ahead and try to find other funding or should I just wait for my admissions decision?