"It doesn't happen in America" and "it's un-American" are not the same statement. On the assumption you're being serious and not facetious, when an American uses the term "un-American," it's meant to mean that the action flies in the face of ideal American values (chiefly freedom).
It's obvious to all of us that these ideals don't reflect reality, but simply accepting that what the American government does is the ideal representation of values the American public actually holds isn't something most of us are willing to do.
It's obvious to all of us that these ideals don't reflect reality, but simply accepting that what the American government does is the ideal representation of values the American public actually holds isn't something most of us are willing to do.