Sometimes what people want is not the right thing to do. Britney's wife may have wanted people to speak out, but I doubt she knows the workings of inter-governmental relationships. Every time someone (out of their good will) said something to publicize her case, it raised her profile and made her more valuable to Putin. Trust me, the US government wishes that the public would butt out.
Some of our "outrage" is manufactured. My point is that Americans are so accustomed to exercising their "freedom of speech" that they fail to ask whether or not it's the most useful thing to do. Thanks to you for reading!