If you've been thinking (as I have) the Germans are silly to complain about the U.S. spying on them, while totally within their rights in punishing the German government official who was working for the CIA, I have found the article for you. James Kirchick writes in The Daily Beast that the U.S. would be foolish not to spy on Germany, and all of our other allies.
Germany, and firms headquartered there, are heavily involved with Russia, Iran, and other nations not friendly to the U.S. Historically, they've been willing to funnel defense-related technology to unfriendly nations willing to pay cash. In fact, Germany could be the poster child for Karl Marx's dictum that capitalists will sell you the rope with which you then hang them.
Instead of apologizing left and right - mostly left - the U.S. should make clear that we keep an eye on everybody: friends, enemies, and neutrals, and will continue doing so because it is in our national interest. We should be equally clear we know they are doing the same surveillance of us, and we intend to prosecute Americans who spy for them.