This is not meant to defend, but rather to explain. Pretty much two things have happened:
The first is that everything is standard now, because everyone's running the same stuff. To spy on the Nazis, the Polish and British had to break the "Enigma" devices that the Germans were using. Nobody in Britain was using these, let alone anywhere but Germany and its allies. Same for Imperial Japan, the Soviet Union, etc. The US breaking the Japanese codes to gain advance knowledge of the attack on Midway couldn't have had any implication against anyone in the USA, because even if we were going to rely on something for privacy, we wouldn't be using classified Japanese military encryption. Today however, not only is encryption in widespread use, but we're all pretty much using the same kinds of encryption and other systems to handle and safeguard our data. Want to break into a computer used by the North Korean/Chinese/Syrian/Iranian/American/British/etc military? They're all going to be running some version of Windows, MacOS, or *NIX, just like pretty much everyone else in the world. The same goes with communications channels. While there are some exceptions, like in China or Russia, most people in the world use the same services and sites (Facebook, Google, Twitter, etc) that people in the USA and the rest of the West do.
Now, all of that would probably be reasonably solvable with some strong oversight and precautions to make sure that any domestic stuff that got pulled in by accident was swiftly and ruthlessly purged, if it weren't for the second factor, which is...
Terrorism and Drugs, aka "The War on." These two combined have had an incredibly corrosive effect on civil liberties. The War on Drugs pretty much has been the single biggest factor in setting law enforcement agencies against the general public, because when large swathes of your populace don't obey (because the laws are stupidly draconian and unrealistic among other things), well, we basically ended up with an attitude that the average person is probably a (drug) criminal. It's worse on the part of some (DEA, looking at you here) than others, and that's before all the incentives like civil asset forfeiture come into play.
What the War on Terrorism did was scare enough people that they tore down what walls there were between law enforcement and intelligence. Remember that bit after 9/11 about how the CIA and FBI didn't compare notes enough? That applies to the DEA, too. It also made a whole new swath of Americans into potential suspects, as well as increasing support among the general public for doing "whatever it takes." Remember, the various agencies (DEA/FBI) were trying to push similar stuff in the past, they just never got as far with it until after 9/11.