Dallas was actually one of the teams to show a profit before.
While some of these stadiums are legitimately in scumblefuck, keep in mind the dynamics of the urban scape vary from city to city. Not every US city is about proximity to downtown, a lot of city cores are complete dumps. Rio Tinto is on the rail line in SLC and not in a bad spot. Chicago has a sub-optimal location but somehow still draws.
I can't foresee the league struggling without a big TV deal providing the salary structure is kept reasonable and some of the other issues surrounding the business side get sorted out.