Americans don't behead innocent people in the streets and don't relentlessly kill people just because they don't share the same religious or political beliefs.
Your comparison is absurd, ignoring the politics of China launching a missile at American soil. The US War in Afghanistan is 17 years old. There were two suicide bombings just three days ago, each killing over 20 people.
Imagine a group of people who want to kill you because of where you were born. Who want to throw you off a building because you're homosexual.
When America kills terrorists, is it equally as bad as when terrorists bomb Americans or Europeans? Is killing in order to police the same as killing out of deep, radical beliefs (and hate)?