Not really "wipe out", but a major civil war will most likely disable America and possibly remove its superpower status; most great powers, ancient or modern, fall for that in the past. America is surrounded by two large ocean. Thus, no country can invade America, mainly because the country will have to build up a military force able to defeat both the Americans' mighty naval fleet and their advanced air force. Of course, doing so will result in an economic collapse for the invading country. Invading the U.S. by crossing the unmilitarized Canadian-American border is the only option, but it is highly unlikely that the U.S. government will allow any foreign military to station in Canada. A nuclear strike probably will not defeat America either, because it is well known that the Americans do have various missile defense systems (Missile Defense Agency).