If all network devices were trivially penetrated by government surveillance, a hypothetical terrorist plot with a WMD has chance A of being discovered. If network devices that are impenetrable to government surveillance are used, I'm not going to argue that the same plot doesn't have < A chance of being discovered (ceteris paribus).
I happen to believe that's a good and just tradeoff to preserve the values of a democratic society, but I accept that others might think otherwise.
The US (and France, and the UK, and everyone else grappling with this that cares to pretend to be a democracy) should absolutely have a thorough, resolute discussion about our options.