1.I believe the GAO report is unduly pessimistic,written by people whose knowledge of satellite navigation is limited.they didn'trelate their predictions to RNP degradation,which is what matters to aviation.
2.Although the USAF (not Army) is responsible for procuring and operating GPS (although not some of the high performance augmentation), the next generation of ATC for commercial aviation (NextGen in US,SESAR in Europe) relies on the twin rocks of GPS and ADS-B.This means that the US government will not allow GPS to fail,perhaps apart from a very minor hiccup.
3.GAO warned of "competion" from Europe (amongst other places), which shows how litle they know.The EU hasn't even let the main contract yet, and they have been faffing about for years. If it wasn't for a relatively small company based at Surrey University, Galileo would have been a no show. The frequency allocation was only temporary,and if the timescale was not met,the communication industry would have gobled it up forever.
4.GPS and Galileo are not in competition if they are mutually compatible
(and they are supposed to be) the more satellites in view, the merrier as far as RNP is concerned
Keith