The United States drone-killed Anwar al Awlaki, an American citizen, because of his speech. I don't disagree with that action, but it does illustrate that there are limits, even in the United States, despite claims to the contrary.
The Wikipedia article gives a different picture. According to US government, "he was centrally involved in planning terrorist operations" and "Yemeni government tried him in absentia in November 2010, for plotting to kill foreigners and being a member of al-Qaeda".
The United States has become an oligarchy over the last few decades. It's basically the worst Western country that you could use as an example of freedom right now.