Terrorism is not new to the United States. As this graphic from the New York Times shows, even in recent decades, we experienced quite a lot of it. In 1970 there were over 400 attacks. However, since 2001, the United States has seen far fewer attacks. Fortunately the Boston Marathon bombing is not as bad as it could have been. But even then, thankfully the bombing is a relative anomaly.
Credit for the piece goes to the graphics department of the Times.