Washington Times reported this morning that the Global Peace Index ranked the United States 85th most peaceful out of 149 countries. Libya was rated 56th, China was 80th, while Israel came in at 144th. Peace was defined as "an absence of violence." Among the factors considered were "prison populations in each nation, the likelihood of violent demonstrations... [and] 'ease of access to small arms and light weapons.'"
Many of the "most peaceful" countries are conveniently covered under the American nuclear umbrella. An interactive map can be found here.