The standard iOS App includes lots of Artwork, e.g. for the CDVCapture plugin.
If you don't use the Capture API (which is likely), you could save 2.3MB by deleting the Capture.bundle in the Resources folder and removing CDVCapture from the Plugins list in the Cordova.plist.

Of course much of the filesize is caused by the various splash screens, icons and maybe artwork you use yourself. There is a very good way to minimize the cost of these. Get ImageOptim and drop your Xcode project folder on it. This will reduce the filesize of your images dramatically (without losing quality). One last step: Xcode recompresses all of the artwork, so they have a bigger filesize again (stupid, right?). Go to the Build Settings tab and type PNG into the search field. Set Compress PNG files to NO.

further reading on imageoptim & Xcode
The whole process should reduce your App by at least 50%, please report back how much you could achieve, thanks.