It is well to consider that this, a country of 300 million people, endures only the highly occasional terrorist act, as seen in Boston, as opposed to the near daily assaults on the populace in other countries that are much smaller.
If you factor out the bombings per capita in this country versus others, it convinces one that we do in fact live in the best place on Earth. We live in a heavily armed country, and yet have a social imperative of tolerance and respect for others; a rather rare juxtaposition of facts.
Though recent events in Boston killed innocents, we have a much lower rate than nearly any other place. Faint praise, perhaps, but still I would rather be here than anywhere.