Cedar Rapid's Trailer on IMDB, and that is definitely some old* b-roll of Philadelphia from somewhere over the Art Museum being passed off as Cedar Rapids, Iowa.
Here's the actual Cedar Rapids skyline for comparison:
*Old, because the Comcast Center is conspicuously missing form the shot meaning two things:
1. The footage is definitely pre-2008 when the Comcast Center was completed, but maybe even older since there's no tower visibly under construction either.
2. The filmmakers saved a buck or two on some outdated, canned footage of a city skyline, still the choice is mystifying for lack of any real good reason to use it. The shot doesn't contribute to the general theme, which I suspect is central to some of the comedic set up of the film, of Cedar Rapids as a bit of a backwater.