Evidence that the US spy agencies engage in large scale espionage on its own people is outrageous. Evidence that US spy agencies engage is foreign espionage is expected.
What is the difference? The US has made explicit commitments to its people through things like the 1st and 4th amendments to protect their privacy.
And this is exactly why more and more non-US-citizen don't like the US anymore. Seeing the world in two classes "US" and "non-US". Yes, I know, no secret service is better. The question is: Are secret services compatible with democracy? More and more indicators let me think: no.
Except the situation we are in, the US spying on both Americans and non-Americans, seems to suggest that they are not at all seeing the world "in two classes" as you claim.
Nobody lives in a true democracy. And it's actually a good thing. Unfortunately the majority of the population is willingly ignorant and refuses to be educated on complex issues. Instead, they have very unbalanced opinions, based almost solely on emotion. It is very easy to harness those emotions and use them to raise to power and then do unspeakable atrocities. Hitler, Musolini to name just a couple.
Everything the government is 100% out in the open (except for ongoing police investigations - but the moment they are finished they are made public). There are only direct elections and almost all decisions are don via general elections. The whole population is well educated on all issues that are subject to politics so they can make informed decisions when voting.
This is of course unfeasible. The only way to make something like that feasible would be to link up our minds like the Borg. Still, the current state is not good enough.
My take on that is that spying is supposed to have as it primary justification the objective of determining a foreign nations true intentions. Its a method to confirm or disprove what is said. Germany, for example, says its no threat to the US, and US spying will hopefully confirm this. And of course vice-versa. So, spying on politicians and policy makers can be argued to be legit. However whole sale spying on citizens is not.
What gone wrong here is that spying is now used for law enforcement, instead of a tool for diplomacy.
The thing is that Germany is a close ally to the US. It's one thing to spy on your ally's leaders to make sure you know what they are up to, but it's another to engage in mass surveillance of their civilian population. The US is doing to friend and foe alike what they have publicly shamed China over.
Spying on citizens of another nation is an act of aggression because it undermines the sovereignty of that nation. If you're outraged to find out the NSA is spying on US citizens, why wouldn't you be outraged to find out the US closest allies (say, Japan, the UK, France, Germany or Canada) are spying on US citizens?
Why should it be acceptable for them to do what would be unacceptable if your own elected representatives did it to you? But undermining the sovereignty of other nations seems to be SOP these days. See US drone strikes in Pakistan or the Russian not-quite-official involvement in the Ukraine.
It's not that what the NSA has been doing is orders of magnitude worse (though some would argue it is), it's the sum of all these things the US has been doing while the presidents and media are continuously cheering for Team America as the One True Beacon of Freedom and Democracy.
Europeans (and Germans in particular) have been uneasy about US politics and how they clash with the country's public image at least since the days after 9/11 (I remember thinking "oh crap, the US will go to war with someone over this") and this is just another drop in the bucket. I guess you react to ultra-nationalism differently if you a have strongly engrained cultural memories of what it's like to be a nation that is "superior" to everyone.
What is the difference? The US has made explicit commitments to its people through things like the 1st and 4th amendments to protect their privacy.