You, as a US citizen, are most certainly protected from my government by the German constitution. Not when it comes to all basic rights in the constitution (only Germans have freedom of movement, freedom of labor and freedom of association), but most are universal and apply to every person.
The US constitution is out of date and simply wrong on this point. Human rights are universal and every human has them. Citizenship shouldn’t come into play. (I really hope that when it comes to freedom of movement, labor and association the limitation on Germans can also be lifted one day. For now the pest of nationalism lives on and makes lifting those limitations a practical impossibility. To me it seems clear that morally it is very wrong to have such limitations.)
Oh, and by the way, breaking moral rules is a hell of a good reason to raise outrage. I don’t understand why you seem to think that something being legal is reason to not be outraged.